Previous tests count for nothing so don't worry about that.
No, it will not show on any records - such RAF records are only maintained for 5 years.
And DON'T TELL THEM!!!
However, if you have any doubts, first of all go down to your local optometrist and try again. If you pass there, book in for your Class 1 Medical at Gatwick but insist on doing the eye examination first - if you fail (and from what you are saying, you should be fine) then stop the Class 1 examination at that point and you should be refunded for all but the eye examination (That's how it used to work, at least).
Interestingly, there is some very credible new research which proves that people can see colours differently at different times of the day and under differing circumstances, including mood, lighting, etc. It is a known fact that certain medications affect colour vision.
Also, the condition of the Ishihara book may have played a part - faded plates are notoriously difficult to discriminate under artificial lighting conditions and the CAA WILL NOT allow you to take the test under natural lighting conditions, even though the test was designed for such. The examiner would have to walk all of ten yards to a window providing natural light........that's asking a bit much.
There are many factors which may have caused you to make an error first time around - many people with normal colour perceptiveness do, which is why the test allows two misreading errors (except in the world of commercial aviation).
The genes which affect colour vision have been known for many years and experiments with Spider Monkeys (Dalton & Sam), whereby they were injected with non-defective genes had remarkable results, in that it 'cured' their colour blindness.
There may be hope for you all yet, although I'm sure the CAA would introduce a rule that says anyone who has been treated with gene therapy is banned from flying, in the same way that you are not permitted to use tinted spectacles which may assist you with colour vision problems. You can wear sunglasses, which impair your ability to detect ALL colours, you can wear vision correcting spectacles, but you can't wear colour correcting spectacles.
