I've asked my hubster to paint mine purple to match the grille bar, the strut bars behind the grille and the S's. My Mini is black and so the contrast with purple is lovely. It's on my IG @Lincolnshireminiowners
Not advisable to fit covers over calipers - if they slip they could get caught in the caliper causing brake issues.
They could cause the brakes to overheat as air cannot get to the pads as easily causing brake fade
Brake dust doesn't get thrown out so builds up between caliper and cover
I used Hammerite smooth to paint mine - nice cheap option