Speak to your local Armed Forces Careers Office. They can get the definitive information from Cranwell for you.
Colour blindness is a definite no-no for controllers, but lots of us wear glasses or contact lenses (especially those of us who worked in pitch black radar rooms back in the day). If your vision is correctable by glasses or lenses, you should be in with a chance.
There is also a list of pre-existing medical conditions that preclude you from joining on the RAF Careers website:
Health checks - RAF Careers
In the end, you will only know by going for selection and getting tested. It is not an examination you can revise for.
