Scale highlights, contrasting colours

Hi everyone
I had an idea, as a hobbyist, I would like to see a way of customizing the colour of highlighted scales which are either in scale or closest to the chosen scale or out of scale
Make them stand out more from the chosen background (mine is gray right now)
Maybe a white for in scale, yellow closest in scale and a red or something for those out of scale
Similar to a set of traffic lights,if that makes sense