I too am slightly red/green deficient. In fact, I couldn't pass the RAF medical because of it. I thought that was the end of the road for me. However, I went to Gatwick, paid about £20 for just the eye part of the class 1 and passed with no major problems.
That was about 9 years ago. I now fly for a large airline (and can see the PAPI's perfectly well thank you
)
Go and get a definate answer from the guys at Caa medical.
Bon chance.