Solarized Osaka is a Neovim colorscheme plugin that implements a Solarized-inspired dark and light theme with extended colors for modern Neovim features and plugin support. The codebase is a monolithic Lua plugin with entry points in `colors/solarized-osaka.lua` and `lua/solarized-osaka/init.lua`. It works by defining a color palette via HSL/HPLUV color space conversions, then generating Neovim highlight groups and optionally producing theme files for external applications (terminals, tmux, fish, etc.) via a template system. The architecture is clean: a config module merges user options, a colors module computes the palette, groups modules define highlight groups per plugin, and a theme module applies them. The plugin has no runtime dependencies beyond Neovim 0.7.2+. Notably, the repository includes standalone implementations of HSL and HSLuv color space conversions (hsl.lua, hsluv.lua) and a utility function for perceptually brightening colors (util.brighten). These components are reusable in other Lua projects. The extras generation system is also well-structured, though tightly coupled to the theme.
onedark.nvim is a Neovim 0.9+ colorscheme plugin implementing the Atom One Dark and One Light themes with Lua and TreeSitter support. The codebase provides 8 theme styles (dark, darker, cool, deep, warm, warmer, light), comprehensive TreeSitter highlight definitions (modern @-prefixed captures), LSP semantic token integration, and support for over 24 plugins (nvim-cmp, telescope, lualine, indent-blankline, etc.). It includes a robust test suite with automated highlight group verification and manual visual testing files. The architecture is modular: palette.lua defines raw color values per style, colors.lua selects and merges with user overrides, highlights.lua maps groups to colors with configurable code styles (italic, bold), and init.lua handles setup/loading/toggling. The utility module provides reusable color blending functions. The repository is actively maintained with frequent releases, detailed changelogs, and responsive issue triage. While primarily a Neovim plugin, its color handling and test patterns could inspire similar theme implementations.