# Change Dynamic Colors (OSC 10 to 19, OSC 110 to 119)
> Set, query and reset the default foreground and background, the cursor's color, and others.
- **Sequence:** `OSC 10 ; 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 a set of *dynamic* colors,
each with its own OSC number:
| `Ps` | Color |
| --- | --- |
| `10` | the default foreground, used by text with no SGR color |
| `11` | the default background |
| `12` | the cursor |
| `13`, `14` | the mouse pointer's foreground and background |
| `15`, `16`, `18` | the Tektronix window's foreground, background and cursor |
| `17`, `19` | the background and foreground of selected text |
`OSC Ps ; Pt ST` sets color `Ps` to `Pt`, in any form X11's `XParseColor`
accepts, and `Pt` of `?` asks for it; the answer is
`OSC Ps ; rgb:rrrr/gggg/bbbb`, ended as the question was. `OSC 1Ps ST`, that
is `OSC 110 ST` to `OSC 119 ST`, puts color `Ps` back as it started.
A sequence can carry more than one color: each further `;` moves on to the
next number, so `OSC 10 ; red ; blue ST` sets the foreground and the
background, and `OSC 10 ; ? ; ? ST` asks for both. An empty one is skipped,
so `OSC 10 ; ; blue ST` sets only the background
([`ChangeColorsRequest`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/misc.c#L3662-L3715),
[`ReportColorRequest`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/misc.c#L3568-L3598),
[`ResetColorsRequest`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/misc.c#L3718-L3753)).
Unlike the palette, neither DECSTR nor RIS resets them.
A program asks for the background, `OSC 11 ; ? ST`, to find out whether it
is running on a light or a dark terminal and choose its own colors to suit.
Where these colors start is the host's choice. The cases are run in a
terminal given a default xterm's: black text on white, with the cursor and
the mouse pointer in the foreground color
([`charproc.c`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/charproc.c#L540-L544)).
That is what the answers below report; it is not how this site draws the
screens.
libghostty-vt has `10`, `11` and `12`, and `110` to `112`. It ignores the
rest, so a question about the mouse pointer goes unanswered, and a chain of
questions that runs past `12` stops there. It also passes over an empty
color without moving on to the next number, so `OSC 10 ; ; blue ST` sets
its foreground. Those cases are known differences.
## Validation
### OSC10-1: Ask for the default colors
Input, one step per line:
```text
\e]10;?\a
\e]11;?\e\\
```
Expected screen:
```text
|____|
reply \e]10;rgb:0000/0000/0000\a\e]11;rgb:ffff/ffff/ffff\e\\
```
### OSC10-2: And the cursor's
Input, one step per line:
```text
\e]12;?\a
```
Expected screen:
```text
|____|
reply \e]12;rgb:0000/0000/0000\a
```
### OSC10-3: Change the foreground
Input, one step per line:
```text
\e]10;#ff8000\a
\e]10;?\a
```
Expected screen:
```text
|____|
reply \e]10;rgb:ffff/8080/0000\a
```
### OSC10-4: Each ; moves to the next color
Input, one step per line:
```text
\e]10;red;blue\a
\e]10;?;?\a
```
Expected screen:
```text
|____|
reply \e]10;rgb:ffff/0000/0000\a\e]11;rgb:0000/0000/ffff\a
```
### OSC10-5: An empty one is skipped
*A known difference: libghostty-vt does not pass this case.*
Input, one step per line:
```text
\e]10;;blue\a
\e]10;?;?\a
```
Expected screen:
```text
|____|
reply \e]10;rgb:0000/0000/0000\a\e]11;rgb:0000/0000/ffff\a
```
### OSC10-6: Questions and changes together
Input, one step per line:
```text
\e]10;?;red\a # ask for 10, set 11
\e]11;?\a
```
Expected screen:
```text
|____|
reply \e]10;rgb:0000/0000/0000\a\e]11;rgb:ffff/0000/0000\a
```
### OSC10-7: Reset
Input, one step per line:
```text
\e]10;red;blue;green\a
\e]110\a
\e]112\a
\e]10;?;?;?\a
```
Expected screen:
```text
|____|
reply \e]10;rgb:0000/0000/0000\a\e]11;rgb:0000/0000/ffff\a\e]12;rgb:0000/0000/0000\a
```
### OSC10-8: RIS leaves them alone
Input, one step per line:
```text
\e]11;red\a
\ec
\e]11;?\a
```
Expected screen:
```text
|____|
reply \e]11;rgb:ffff/0000/0000\a
```
### OSC10-9: The mouse pointer
*A known difference: libghostty-vt does not pass this case.*
Input, one step per line:
```text
\e]13;?\a
```
Expected screen:
```text
|____|
reply \e]13;rgb:0000/0000/0000\a
```
### OSC10-10: A chain past the cursor
*A known difference: libghostty-vt does not pass this case.*
Input, one step per line:
```text
\e]12;?;?\a # the cursor, then the pointer
```
Expected screen:
```text
|____|
reply \e]12;rgb:0000/0000/0000\a\e]13;rgb:0000/0000/0000\a
```
---
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 .