Owenrules - in reply to your question about passing a medical and later failing retests after forking out a fortune, well the colour vision test only needs to be taken at your initial medical, so you will not be tested for it again. You can obvioustly fail further medicals due to other problems, but thats not what we are concerned about here.
A word of caution. The CAA thinks colour vision never changes so if you take a class 1 and fail - they will not allow a retest, but you can get only the colour vision test done.
Why not try the City Uni tests to see exactley what you are likely to pass and where, not bad for £75.
Welcome to the forum and I wish you all the best with your future flying.