Monobiome

monobiome is a minimal, balanced color palette for use in terminals and text editors. It was designed in OKLCH space to achieve perceptual uniformity across all hues at various levels of luminance, and does so for eight monotone bases and eight accent colors (plus one zero chroma default base). Each of the monotone base colors (named according to a natural biome whose colors they loosely resemble) are designed to achieve identical contrast with the accents, and thus any one of the options can be selected to change the feeling of downstream themes without sacrificing readability.

(Preview of light and dark alpine theme variants)

The name "monobiome" connects the palette to its two key sources of inspiration:

• mono-: monobiome is inspired by the monoindustrial theme, and attempts to extend and balance its accents while retaining similar color identities.
• -biome: the desire for several distinct monotone options entailed finding a way to ground the subtle color variations that were needed, and I liked the idea of tying the choices to naturally occurring environmental variation like Earth's biomes (even if it is a very loose affiliation, e.g., green-ish = grass, basically).

Palette

The monobiome palette is fundamentally a set of parameterized curves in OKLCH color space. Each color identity has one monotone curve and one accent curve, both of which have fixed hue values and vary from 10% to 98% lightness. Monotone curves have fixed chroma, whereas the accent curves' chroma varies smoothly as a function of lightness within sRGB gamut bounds.

Chroma curves	Color trajectories

Palette

Chroma curves are designed specifically to establish a distinct role for each accent and are non-intersecting over the lightness domain (hence the distinct "bands" in the above chroma curve figure). There are eight monotone-accent pairs, plus a single grey trajectory:

Monotone / biome	Accent color	Hue
alpine	grey	n/a
badlands	red	29
chaparral	orange	62.5
savanna	yellow	104
grassland	green	148
reef	cyan	205
tundra	blue	262
heathland	violet	306
moorland	magenta	350

The alpine/grey curve has zero chroma (and is thus invariant to hue), varying only in lightness from dark to light grey.

Themes

Dark themes	Light themes

Themes are derived from the monobiome palette by selecting a monotone base (the "biome"), a base lightness, and a contrast level. Although one can use arbitrary contrast metrics, OKLCH distance (Euclidean distance in OKLab) is designed to capture perceptual distinction. As such, perceptually uniform themes under arbitrary monotones can be generated by calculating the accent colors equidistant from that base. This is equivalent to determining the points at which a sphere centered at the monotone base intersects with the accent curves; the radius of such a sphere effectively determines the theme contrast, and the colors on the sphere surface are equally perceptually distinct relative to the background.

The following plots show the intersection of the sphere centered at a fixed background color (alpine biome with a lightness of 20) under variable radii:

	-l 20 -d 0.3	-l 20 -d 0.4	-l 20 -d 0.5
Color visualization
Editor preview

In short, the base lightness (-l) dictates the brightness of the background, and the contrast (-d) controls how perceptually distinct the accent colors appear with respect to that background. These are free parameters of the monobiome model: themes can be generated under arbitrary settings that meet user preferences.

Generation

When generating full application themes, fixed lightness steps are used in the chosen monotone trajectory to establish consistent levels of distinction between background layers. For example, the following demonstrates how background and foreground elements are chosen for the monobiome vim/neovim themes:

Note how theme elements are mapped onto the general identifiers bg0-bg3 for backgrounds, fg0-fg3 for foregrounds, and gray for a central gray tone. The relative properties (lightness differences, contrast ratios) between colors assigned to these identifiers are preserved regardless of biome or harshness (e.g., bg3 and gray are always separated by 20 lightness points in any theme). As a result, applying monobiome themes to specific applications can effectively boil down to defining a single "relative template" that uses these identifiers, after which any user-provided parameters can be applied automatically.

The full palette \rightarrow scheme \rightarrow template \rightarrow theme pipeline can be seen in detail below:

This figure demonstrates how kitty themes are generated, but the process is generic to any palette, scheme, and app. This implemented in two stages using the monobiome CLI:

• First generate the scheme file, the definitions that respect perceptual uniformity of accents with respect to the base monotone:

  monobiome scheme dark grassland -d 0.42 -l 20 -o scheme.toml
  

  This calculates the accents a distance of 0.42 units in Oklab space from the grassland monotone base at a lightness of 20, and writes the output to scheme.toml.

• Then populate the scheme file with concrete palette colors and push it through an app config template:

  monobiome fill scheme.toml templates/kitty/active.theme -o kitty.theme
  

  This writes a concrete theme to kitty.theme that matches the user preferences, i.e., the contrast (-d), background lightness (-l), mode (dark), and biome (grassland). Every part of this process can be customized: the scheme parameters, the scheme definitions/file, the app template.

Running these commands in sequence from the repo root should work out-of-the-box, after having installed the CLI tool.

The monobiome CLI produces the scheme file for requested parameters, and the symconf CLI pushes palette colors through the scheme and into the app templates to yield a concrete theme.

Applications

This repo provides palette-agnostic theme templates for kitty, vim/neovim, and fzf in the templates/ directory. Pre-generated concrete themes can be found in app-config/, if you'd like to try an example out-of-the-box without using the monobiome CLI. Raw palette colors can be found in colors/ if you want to use them to define static themes for other applications.

Themes files in the app-config/ directory are generated for light and dark modes of each biome, and named according to the following pattern:

<biome>-monobiome-<mode>.<filename>

One can set these themes for the provided applications as follows:

• kitty

  Find kitty themes in app-config/kitty. Themes can be activated in your kitty.conf with

  include <theme-file>
  

  Themes are generated using the kitty theme template.

• vim/neovim

  Find vim/neovim themes in app-config/nvim. Themes can be activated by placing a theme file on Vim's runtime path and setting it in your .vimrc/init.vim/init.lua

  with

  colorscheme <theme-name>
  

  Themes are generated using the vim theme template.

• fzf

  In app-config/fzf, you can find scripts that can be ran to export FZF theme variables. In your shell config (e.g., .bashrc or .zshrc), you can source these files to apply them in your terminal:

  source <theme-file>
  

  Themes are generated using the fzf theme template.

• Firefox

  Firefox themes for all monotone backgrounds are publicly listed as Mozilla add-ons, and switch between light/dark schemes based on system settings. You can also download raw XPI files for each theme in app-config/firefox/, each of which is generated using the Firefox manifest.json template.

  Static light and dark themes are additionally available (i.e., that don't change with system settings).

  

CLI installation

A brief theme generation guide was provided in the Generation section, making use of the monobiome CLI. This tool can be installed from PyPI, using uv/pipx/similar:

uv tool install monobiome
# or
pipx install monobiome

The monobiome has provides three subcommands:

• monobiome palette: generate palette files from raw parameterized curves

  usage: monobiome palette [-h] [-n {hex,oklch}] [-f {json,toml}] [-o OUTPUT]
  
  options:
    -n {hex,oklch}, --notation {hex,oklch}
                          color notation to export (either hex or oklch)
    -f {json,toml}, --format {json,toml}
                          format of palette file (either JSON or TOML)
    -o OUTPUT, --output OUTPUT
                          output file to write palette content
  

• monobiome scheme: generate scheme files that match perceptual parameters

  usage: monobiome scheme [-h] [-m {wcag,oklch,lightness}] [-d DISTANCE] [-o OUTPUT] [-l L_BASE]
                          [--l-step L_STEP] [--fg-gap FG_GAP] [--grey-gap GREY_GAP]
                          [--term-fg-gap TERM_FG_GAP]
                          {dark,light}
                          {alpine,badlands,chaparral,savanna,grassland,reef,tundra,heathland,moorland}
  
  positional arguments:
    {dark,light}          scheme mode (light or dark)
    {alpine,badlands,chaparral,savanna,grassland,reef,tundra,heathland,moorland}
                          biome setting for scheme.
  
  options:
    -m {wcag,oklch,lightness}, --metric {wcag,oklch,lightness}
                          metric to use for measuring swatch distances.
    -d DISTANCE, --distance DISTANCE
                          distance threshold for specified metric
    -o OUTPUT, --output OUTPUT
                          output file to write scheme content
    -l L_BASE, --l-base L_BASE
                          minimum lightness level (default: 20)
    --l-step L_STEP       lightness step size (default: 5)
    --fg-gap FG_GAP       foreground lightness gap (default: 50)
    --grey-gap GREY_GAP   grey lightness gap (default: 30)
    --term-fg-gap TERM_FG_GAP
                          terminal foreground lightness gap (default: 60)
  

• monobiome fill: produce concrete application themes from a given scheme and app template

  usage: monobiome fill [-h] [-p PALETTE] [-o OUTPUT] scheme [template]
  
  positional arguments:
    scheme                scheme file path
    template              template file path (defaults to stdin)
  
  options:
    -p PALETTE, --palette PALETTE
                          palette file to use for color definitions
    -o OUTPUT, --output OUTPUT
                          output file to write filled template