IO540,
I can get a CAA IMC rating. In fact, somebody with a CAA PPL can used to be able to get a CAA IR with colour blindness. It's the JAA that's

everything up!
Specifically, my JAA medical is stamped VDL (Vision Distance Limitation - must wear corrective lenses, etc.) and VCL (Vision Colour Limition) which reads "VFR flights by daytime only". Hence no IFR flights. However, the VFR restriction has now been lifted and I can get an IMC - hence the original question!
Daytime only I can understand, but one has to wonder why, if I am boggling around inside a cloud with zero vis, I need to be able to identify aircraft nav lights. After all, I'm not going to see the damned thing until I bump into it!
TPK