This kind of feature is pretty rare for Racing Games in general, and I’d like to see another title add it in: Tachometer Colours for each Car.
Basically, being able to change the colour of the Tachometer’s parts, including its background, numbers and the rev gauge. It could even apply to other parts of the in-race HUD.
Personally, I find that this could add more personality to the driving experience of each customized Car, having the Tachometer be in the same colour as the main colour of the Car itself.