I don't think he wants it as a default change for everyone, but rather as a toggle for those that are colourblind.
Drastic colour changes for clarity in that special case would certainly be nice to have for them.
Accessibilty is a difficult thing to add (properly) unless you are experienced in that field.
Floating icons could be very immersion breaking though, I think playing with the colours to find good combinations for colourblind people (covering most or all colourblind conditions) would be a good way to implement this over a floating icon toggle.