Appearance
Underline color (SGR 58)
SGR 58 sets the underline color independently of the text foreground color. The syntax mirrors SGR 38 (foreground):
ESC [ 58:2::R:G:B m for truecolor, ESC [ 58:5:N m for 256-color. Reset the underline color to default with SGR 59.
This is particularly useful with curly underlines (SGR 4:3) for diagnostic indicators: red underline for errors, yellow for warnings, blue for hints — all while keeping the text color unchanged. Introduced by Kitty and adopted by other modern terminals.Supported by 1 of 6 backends (17%)
Support Matrix
| Backend | Version | Support | Notes |
|---|---|---|---|
| xterm.js | 5.5.0 | ✓ yes | |
| Alacritty | 0.26.0 | ~ partial | Not exposed via alacritty_terminal API |
| Ghostty | 1.3.1 | ~ partial | Underline color not exposed via native Zig API |
| Kitty | 0.40.0 | ~ partial | Not exposed via Python batch bridge |
| WezTerm | 0.1.0-fork.5 | ~ partial | Not exposed via wezterm-term API |
| vt100 | 0.1.0 | ✗ no | Not implemented — pure TypeScript emulator |