Fibreglass boats are often painted (hull and topsides) with no problems. Most clear coats are just paint without pigment. FB is quite correct in his post...fibreglass boats and carbon fibre bikes are indeed built in a similar manner.
I finished my shipwrights apprenticeship 38 years ago. I really couldn't count the number of fibreglass boats I've painted.
You will probably get a poor finish from a rattle can. It's unlikely that a rattle can finish will be as durable as the original finish. A two pack finish from a professional spray painter would be better, obviously.Two pack will go over carbon fibre quite well and won't damage the resin.