Try calling some AME's as well... Tell them you wanna take color vision before continuing with the rest of the medical exam... Call ahead to find out which test they use at that office.
No, actually you want to schedule a
consultation. If you start the exam the test is on the record. If you fail, you start sliding ...
CONSULT, then take the Ishihara under normal lighting - not fluorescent. I'm thinking you'll do okay; the test wasn't designed for fluorescent light and this seems to make the test harder.
If you have trouble then you may have to find an alternate test, just as you've been doing.
Now the AOPA medical forum is a different animal. A couple of AME's (members, not AOPA employees) are on there a lot and can help you. They deal with this sort of thing frequently and are up to speed on it - unlike AOPA itself, apparently. If you're a member then try this first and follow their advice. I'm certainly not an expert.