Thank you for adding support for UnderlineColor and UnderlineStyle.

I tried it, and in gnome-terminal, the UnderlineStyle change works, but the UnderlineColor color doesn't seem to work.
The gnome-terminal itself supports UnderlineColor, so it should reflect the underline color, for example, by running the following command:

TERM=xterm-ghostty go run ./_demos/style.go

Environment:

Ubuntu 24.04
gnome-terminal 3.52.0-1ubuntu2