Change the palette.
data is string of 7 hex digits. The first digit is the color number to change, and the rest are RRGGBB.
🛈 beeps, but does not confuse the parser in default configuration.
🛆 When using the fbcon driver the reset palette only applies to cells drawn after this sequence.
iterm2: properly uses ESC \ to terminate the sequence, adds additional supported colors, recommends to use (used by other terminals) instead.