Prior to 2.1/2.2 (I don't know exactly which, I think it varies on the issue), there was a greater array of visual variety in the game than at present, notably for player equipment. I never saw these changes as being mentioned as deliberate, so have put it in bug reports for now (can be moved to brain port if necessary). Anyway, issues are:
Power Armour used to come in a wide variety of different appearances: varying shades of blue and red for PPU and APU, varying shades of blue and grey-white for MC and HC, Plain and outlined for PE RC and PE PC. PA4 was also distinctive colours - purple for monks and black for PE. All that has gone, which is a real shame.
Weapon effects: Chaos Queen Flameavalanche used to use the same effect as reaperspiders/chaos queen. Mos raygun pistols and rifles used to use a purple beam effect, with those bought from TG FSM (and those used by DoY guards) being notable for their red colour (all appear to now be red beams). The Ravager used to be distinct from other Plasma waves by it's cyan beam.
Be good to see all this (especially PA patterning) restored.