Porches insistence on keeping red or yellow calipers dependent on what brakes you chose makes so many colour combos look a bit wrong to my eyes (red car and red calipers is fine but what if you want ceramics, yellow calipers on a red car look crap!)
Given the range of options for other things I'm surprised they won't let you chose caliper colour and pay for it, Ferrari and mclaren will.
Truly a first world problem, of course, but if I was in the position to buy a gt4 I'd want a carmine red one with ceramics but the yellow calipers offend my eyes when the car is that colour!