I did my alternate test at the FSDO with the light gun signals (don't know if this is an accepted test anymore). Anyways, I have a Letter of Evidence and just show that to the AME at each medical.

When I did my medical for Delta and it came to the color test, I just showed the Doc my letter and that sufficed.

Interestingly enough, my new AME has new plates and has me take them "just for fun" and I get about 4-5 out of 6. Easier than the old plates but I'm glad to have the LOE so that I don't have to rely on passing the plate test each year.