MorningHue

Code Examples

MorningHue highlights all standard Vim syntax groups, so any language Vim supports works automatically. Here are examples from several languages commonly used in hardware verification and software development.

SystemVerilog

alu_scoreboard.sv

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`include "uvm_macros.svh" `define TIMEOUT 1000 module alu_scoreboard #(parameter int WIDTH = 32) ( input logic clk, input logic rst_n, input logic [WIDTH-1:0] a, b, output logic [WIDTH-1:0] result ); logic [WIDTH-1:0] expected; always_comb begin case (opcode) 3'b000: expected = a + b; 3'b001: expected = a - b; default: expected = '0; endcase end assert property (@(posedge clk) result === expected) else $error("Mismatch: got %h, exp %h", result, expected); endmodule

Python

regression.py

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import subprocess from pathlib import Path MAX_PARALLEL = 8 def run_regression(test_dir: str, seed: int = 42) -> bool: """Execute a full regression run.""" test_path = Path(test_dir) if not test_path.exists(): raise FileNotFoundError(f"Test dir missing") for cfg in test_path.glob("*.cfg"): result = subprocess.run(["simv", "+seed=" + str(seed)]) return True

C

driver.c

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#include <stdio.h> #include <stdlib.h> #define BUF_SIZE 1024 int process_data(const char *input, size_t len) { char buffer[BUF_SIZE]; if (input == NULL || len == 0) { return -1; } printf("Processing %zu bytes\n", len); return 0; }

Makefile

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# Simulation build targets VCS_HOME := /tools/synopsys/vcs/R-2023.12 SEED := 42 compile: filelist.f $(VCS_HOME)/bin/vcs -sverilog -f filelist.f sim: compile ./simv +ntb_random_seed=$(SEED)

TCL

run_sim.tcl

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# Simulation run script proc run_test {testname seed} { set logfile "logs/${testname}_${seed}.log" if {[file exists $logfile]} { file delete $logfile } puts "Running: $testname with seed $seed" source "configs/${testname}.tcl" }

Bash / Shell

run_tests.sh

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#!/bin/bash PROJ_DIR="/home/user/verification" NUM_SEEDS=10 for seed in $(seq 1 $NUM_SEEDS); do echo "Running seed: $seed" if ! ./simv +seed=$seed; then echo "FAILED at seed $seed" >&2 fi done

JSON

config.json

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{ "testbench": "alu_tb", "num_tests": 1000, "coverage": true, "timeout_ns": 50000, "debug": false, "seed": null }

Markdown

README.md

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# ALU Verification This project contains the UVM testbench for the ALU module. ## Getting Started `make compile` followed by `make sim` to run. [Documentation](https://example.com)

Accessibility & Contrast Ratios

All contrast ratios are calculated against the background (#F1EDE5, luminance 0.849) using the WCAG 2.1 formula. Colors are sorted by contrast ratio.

Hex	cterm	Contrast Ratio	Grade	Usage
`#0000d7`	20	9.08 : 1	AAA	Keyword, module, structure
`#870000`	88	8.86 : 1	AAA	PreProc, `define, `ifdef
`#444444`	238	8.33 : 1	AAA	Normal text
`#870087`	90	7.56 : 1	AAA	Control flow, always, if
`#5f00d7`	56	7.29 : 1	AAA	Type, StorageClass
`#005f00`	22	6.82 : 1	AA	String
`#005f5f`	23	6.42 : 1	AA	Boolean, tag
`#af0000`	124	6.37 : 1	AA	Error, exception
`#005f87`	24	6.06 : 1	AA	Function, Identifier
`#005faf`	25	5.52 : 1	AA	Operator, delimiter
`#875f00`	94	4.90 : 1	AA	Number, constant
`#af00d7`	128	4.73 : 1	AA	Statement, assert
`#d70000`	160	4.62 : 1	AA	Import, include
`#949494`	246	2.60 : 1	Subtle	Comment (italic)
`#1c1c1c`	—	16.29 : 1	AAA	ANSI color15 (bright white) — remapped for TUI tool visibility

* ANSI palette slots color7 (#444444, listed above as Normal text) and color15 (#1c1c1c) are remapped to dark values. On a light background, tools like GitHub Copilot CLI render text in these slots; keeping them light would make the output invisible.

Why Accessibility Matters for Code

Engineers spend hours reading code on screen. A theme with poor contrast forces the eyes to work harder, leading to fatigue and missed details. MorningHue ensures:

Keywords and types are immediately visible at AAA (7:1+), so structural boundaries are never missed
All other syntax meets AA (4.5:1+), the WCAG minimum for normal text
Comments are intentionally subtle so they don't compete with active code
Warm background reduces glare compared to pure white, especially in well-lit offices

Comparison with PaperColor

PaperColor is an excellent theme, but several of its colors fall below the WCAG AA threshold on its own background. MorningHue addresses every one:

Element	PaperColor	CR	MorningHue	CR	Change
Background	`#eeeeee`	—	`#F1EDE5`	—	Warmer, less harsh
Strings	`#5f8700`	3.65	`#005f00`	6.82	+87%
Statement	`#d70087`	4.27	`#af00d7`	4.73	+11%
Operator	`#0087af`	3.56	`#005faf`	5.52	+55%
Numbers	`#d75f00`	3.28	`#875f00`	4.90	+49%
Boolean	`#008700`	4.05	`#005f5f`	6.42	+59%
Broken symlinks	Invisible		Bold red on pink		Fixed

Why a Light Theme?

MorningHue is designed for brightly-lit environments. There is peer-reviewed research supporting this design choice — but the picture is nuanced. This section presents what the evidence actually says.

The positive polarity advantage

Polarity is the term researchers use for the relationship between text and background luminance. Positive polarity means dark text on a light background; negative polarity means light text on a dark background.

Multiple controlled studies find that positive polarity produces better proofreading accuracy and faster reading speed under typical office lighting. The clearest mechanistic explanation is optical, not perceptual: a bright background causes the pupil to constrict. Smaller pupils reduce spherical and chromatic aberrations in the eye's lens, producing a sharper retinal image. A 2014 study by Piepenbrock, Mayr, and Buchner directly measured smaller pupil sizes and better performance with positive polarity displays.¹ The same group found the effect was more pronounced with smaller character sizes² — relevant for code, where identifiers and operators are often small.

Importantly, a 2007 study by Buchner and Baumgartner⁴ found that when display luminance was equalized between the two polarity conditions, the performance difference disappeared. The advantage is a luminance effect, not a polarity effect per se. In normal use, positive polarity displays are brighter overall, and it is that extra luminance — driving pupil constriction — that produces the reading benefit.

Positive polarity

int

result = 42;

Bright bg → pupil constricts
→ sharper retinal image

Negative polarity

int

result = 42;

Dark bg → pupil dilates
→ more optical aberration

Ambient light is the key variable

The advantage is conditional on environment. A 2024 study⁵ found that under high ambient brightness, negative polarity actually produced lower eye fatigue — the dark screen reduces total luminance load when the room itself is already very bright. Research by Dobres et al. (2017)⁶ consistently shows that what matters most is matching screen luminance to ambient light: when screen brightness is close to the environmental brightness, visual fatigue is reduced regardless of polarity.

Design rationale: MorningHue is designed for bright offices and indoor workspaces where ambient and screen luminance are naturally similar — the context where the positive polarity advantage is most consistent and most measured.

Warm white, not pure white

Pure white backgrounds (#ffffff) maximize the luminance benefit but can introduce halation — a perception of light "bleeding" into surrounding dark text, especially noticeable for users with astigmatism. The warm off-white background of MorningHue (#F1EDE5) retains enough luminance to drive pupil constriction while reducing the harshness that makes extended reading on pure-white screens uncomfortable.

When a dark theme is the right choice

The research does not support positive polarity as universally superior. Dark themes are a legitimate choice in several contexts:

Dim or dark environments — dark themes reduce glare and better match low ambient luminance, where the positive polarity advantage disappears or reverses
Individual differences — polarity effects vary significantly between people; population studies show each polarity benefits a comparable proportion of individuals
Perceived cognitive workload — a 2025 ACM CHI eye-tracking study⁷ found dark mode produced significantly lower perceived workload on complex visual tasks
Low contrast sensitivity — users with certain vision conditions, low vision, or cataracts may read faster with negative polarity
Personal preference — a theme you find comfortable is better than one you merely tolerate

There is also no peer-reviewed research specifically on dark vs light themes for code reading. Any claim that one polarity is objectively better for programming goes beyond the available evidence.

Sources

Piepenbrock, C., Mayr, S., & Buchner, A. (2014). Smaller pupil size and better proofreading performance with positive than with negative polarity displays. Ergonomics, 57(11), 1670–1677. pubmed.ncbi.nlm.nih.gov/25135324
Piepenbrock, C., Mayr, S., Mund, I., & Buchner, A. (2013). Positive display polarity is advantageous for both younger and older adults. Ergonomics, 56(7), 1116–1124. doi:10.1080/00140139.2013.790485
Piepenbrock, C., Mayr, S., & Buchner, A. (2014). Positive display polarity is particularly advantageous for small character sizes. Human Factors, 56(5), 942–951. doi:10.1177/0018720813515509
Buchner, A., & Baumgartner, N. (2007). Text–background polarity affects performance irrespective of ambient illumination and colour contrast. Ergonomics, 50(7), 1036–1063. pubmed.ncbi.nlm.nih.gov/19562598
Eichenbaum et al. (2024). Effects of ambient illuminance on display polarity, visual fatigue, and reading performance. BMC Ophthalmology / PMC. pmc.ncbi.nlm.nih.gov/articles/PMC11175232
Dobres, J., Chahine, N., & Reimer, B. (2017). Perceptual and legibility thresholds for positive and negative polarity text in indoor and outdoor environments. Applied Ergonomics, 65, 41–47. doi:10.1016/j.apergo.2016.08.011
Wang, Y. et al. (2025). The dark side of dark mode: an eye-tracking study. ACM CHI 2025. doi:10.1145/3715669.3725879

Installation

VS Code

Clone into your VS Code extensions directory:

# Linux / macOS git clone https://github.com/glenzac/morninghue-theme ~/.vscode/extensions/morninghue # Windows git clone https://github.com/glenzac/morninghue-theme %USERPROFILE%\.vscode\extensions\morninghue

Then restart VS Code, open the Command Palette (Ctrl+Shift+P), type Preferences: Color Theme, and select MorningHue.

Vim / Neovim

mkdir -p ~/.vim/colors cp colors/morninghue.vim ~/.vim/colors/

Add to ~/.vimrc:

set background=light colorscheme morninghue

iTerm2 (macOS)

Open iTerm2 → Preferences → Profiles → Colors
Click Color Presets… → Import… and select morninghue.itermcolors
Select MorningHue from the Color Presets dropdown

zsh prompt theme

oh-my-zsh:

cp morninghue.zsh-theme ~/.oh-my-zsh/themes/morninghue.zsh-theme

Set ZSH_THEME="morninghue" in ~/.zshrc.

Standalone:

source /path/to/morninghue.zsh-theme # add to ~/.zshrc

The prompt uses ANSI palette colors — combine with the iTerm2 preset so the prompt accents automatically match the theme's exact hues.

xterm (.Xresources)

cp morninghue.Xresources ~/.Xresources xrdb -merge ~/.Xresources

ANSI palette slots color7 and color15 are remapped to dark values so TUI tools like GitHub Copilot CLI render text visibly on the light background. Several bright slots are also semantically remapped — see the ANSI palette table.

tmux

Add to ~/.tmux.conf:

source-file /path/to/morninghue.tmux.conf

dircolors (fixes broken symlinks)

Add to your shell rc file:

# bash / zsh [ -f /path/to/morninghue.dircolors ] && eval $(dircolors /path/to/morninghue.dircolors) # tcsh / csh if ( -f /path/to/morninghue.dircolors ) eval `dircolors -c /path/to/morninghue.dircolors`

Color Palette

Background & Foreground

AAA Tier — CR ≥ 7:1

AA Tier — CR ≥ 4.5:1

Code Examples

SystemVerilog

Python

C

Makefile

TCL

Bash / Shell

JSON

Markdown

UI Elements

Vim Statusline

tmux Status Bar

Diagnostics & Selection

Diff View

Broken Symlinks (ls --color)

Accessibility & Contrast Ratios

Why Accessibility Matters for Code

Comparison with PaperColor

Why a Light Theme?

The positive polarity advantage

Ambient light is the key variable

Warm white, not pure white

When a dark theme is the right choice

Sources

Installation

VS Code

Vim / Neovim

iTerm2 (macOS)

zsh prompt theme

xterm (.Xresources)

tmux

dircolors (fixes broken symlinks)