Closes https://github.com/ppy/osu/issues/14669.
Colour{Display,Palette}
Colour4
LabelledDrawable
OsuColour
Will be removed once combo colours are mutable.
Logic is shared with the timeline blueprints which also have the same problem of displaying text on top of a combo colour. Slightly modified the formula. Seems to yield better results on a subjective check.
Ensure setup screen text boxes commit on losing focus