OSC 13 Pointer Foreground Color
Set and query the color of the mouse pointer, while it is over the window.
OSC 13 ; Pt ST
OSC 13 ; Pt ST sets the color of the mouse pointer, while it is over the window, and OSC 13 ; ? ST asks what it is. OSC 113 puts it back as it started. It is one of xterm’s dynamic colors, and works as OSC 10 explains: Pt is any color X11 can parse, and a further ; in the same sequence moves on to color 14.
The two pointer colors are the X cursor’s: an X cursor shape is drawn in two colors, a foreground and an outline around it. OSC 22 chooses the shape.
A default xterm starts it as the pointerColor resource, which is the foreground (charproc.c), so in the terminal the cases run in, set up as a default xterm, it is reported as rgb:0000/0000/0000.
libghostty-vt has no such color, and ignores OSC 13 and OSC 113, so the cases that ask are known differences.
Validation
OSC13-1: Ask for it
\e]13;?\a
|____|
reply \e]13;rgb:0000/0000/0000\a
OSC13-2: Change it
\e]13;#0080ff\a
\e]13;?\a
|____|
reply \e]13;rgb:0000/8080/ffff\a
OSC13-3: Nothing on screen
A
\e]13;red\a
B
|AB__|
cursor 1,3