# Special Colors (OSC 5)
> Set and query the colors xterm can draw bold, underlined, blinking, reversed and italic text in.
- **Sequence:** `OSC 5 ; Pc ; Pt ST`
- **ECMA-48:** [§8.3.89 OSC – Operating System Command, p. 51](https://archive.org/details/ecma-48-5th-edition-june-1991/page/n64/mode/1up)
- **xterm:** [Operating System Commands](https://invisible-island.net/xterm/ctlseqs/ctlseqs.html)
Besides the [palette](https://control-codes.page/osc/palette/index.html.md), xterm has five *special* colors, which
it can use to show an attribute as a color instead of, or as well as, the
attribute itself:
| `Pc` | Resource | Used for |
| --- | --- | --- |
| `0` | `colorBD` | bold |
| `1` | `colorUL` | underline |
| `2` | `colorBL` | blink |
| `3` | `colorRV` | reverse |
| `4` | `colorIT` | italic |
`OSC 5 ; Pc ; Pt ST` sets one, `Pt` of `?` asks for it, and
[`OSC 105 ; Pc ST`](https://control-codes.page/osc/reset-special-colors/index.html.md) puts it back, exactly as
[OSC 4](https://control-codes.page/osc/palette/index.html.md) and [OSC 104](https://control-codes.page/osc/reset-palette/index.html.md) do for the palette; they are also palette numbers 256 to 260, so
`OSC 4 ; 256 ; ? ST` asks for the bold color too
([`do_osc`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/misc.c#L4190-L4196),
[`ReportAnsiColorRequest`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/misc.c#L2636-L2659)).
Each is used only when its mode is on, which [OSC 6](https://control-codes.page/osc/color-mode/index.html.md)
turns on and off, and all five modes are off by default. Each starts as the
default foreground
([`charproc.c`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/charproc.c#L666-L672)),
so in a terminal set up as a default xterm, as the cases are, each is
reported as black.
libghostty-vt has no special colors, and ignores `OSC 5` and palette numbers
past 255, so the cases that ask are known differences.
## Support
| Terminal | Version | Support | Notes |
| --- | --- | --- | --- |
| VT220 | [manual](https://vt100.net/docs/vt220-rm/), 2nd ed., 1984 | No | OSC is not among the controls it recognizes ([§4.2](https://vt100.net/docs/vt220-rm/chapter4.html#S4.2)) |
| VT510 | [manual](https://vt100.net/docs/vt510-rm/), 1st ed., 1993 | No | ignores an OSC string ([chapter 4](https://vt100.net/docs/vt510-rm/chapter4.html)) |
| xterm | patch 412, [xterm-411a](https://github.com/ThomasDickey/xterm-snapshots/tree/xterm-411a) | Yes | used only when OSC 6 turns each on |
| libghostty-vt | [0f171f6](https://github.com/ghostty-org/ghostty/tree/0f171f650a1cbbd6df4a2573b6b0c7de57cc6d90) | No | no special colors (OSC5-1, OSC5-2) |
| Konsole | 26.11.70, [a24c3d71](https://invent.kde.org/utilities/konsole/-/tree/a24c3d71be3684f24d030aa2dbe9bd723d985233) | No | not in its source |
| kitty | 0.49.1, [run in a VM](https://git.jcollie.dev/jeff/control-codes/src/branch/main/emulators/results/kitty.json) | No | fails the case that shows it working |
| foot | 1.28.0, [run in a VM](https://git.jcollie.dev/jeff/control-codes/src/branch/main/emulators/results/foot.json) | No | fails the case that shows it working |
| pyte | 0.8.2, [run as a library](https://git.jcollie.dev/jeff/control-codes/src/branch/main/emulators/results/pyte.json) | No | fails the case that shows it working |
| xterm.js headless | 6.0.0, [run as a library](https://git.jcollie.dev/jeff/control-codes/src/branch/main/emulators/results/xtermjs.json) | No | fails the case that shows it working |
| alacritty_terminal | 0.26.0, [run as a library](https://git.jcollie.dev/jeff/control-codes/src/branch/main/emulators/results/alacritty.json) | No | fails the case that shows it working |
| ConEmu | build 230724, its [documentation](https://conemu.github.io/en/AnsiEscapeCodes.html) | No | not in its [ANSI escape codes](https://conemu.github.io/en/AnsiEscapeCodes.html) |
| rxvt-unicode | 9.31, [run in a VM](https://git.jcollie.dev/jeff/control-codes/src/branch/main/emulators/results/urxvt.json) | No | fails the case that shows it working |
| VTE | 0.84.1, [run as a library](https://git.jcollie.dev/jeff/control-codes/src/branch/main/emulators/results/vte.json) | No | fails the case that shows it working |
## Validation
### OSC5-1: The color for bold
*A known difference: libghostty-vt does not pass this case.*
Input, one step per line:
```text
\e]5;0;?\a
```
Expected screen:
```text
|______|
reply \e]5;0;rgb:0000/0000/0000\a
```
### OSC5-2: Set, and asked for through OSC 4
*A known difference: libghostty-vt does not pass this case.*
Input, one step per line:
```text
\e]5;1;#ff0000\a # the color for underline
\e]4;257;?\a
```
Expected screen:
```text
|______|
reply \e]4;257;rgb:ffff/0000/0000\a
```
### OSC5-3: Nothing on screen
Input, one step per line:
```text
A
\e]5;0;red\a
B
```
Expected screen:
```text
|AB____|
cursor 1,3
```
---
This is the Markdown version of . On that page every validation case runs live in libghostty-vt, the terminal emulation core of Ghostty, compiled to WebAssembly.
The validation cases are written in the notation described in .