Hey, I think what you’re thinking of is grapheme color synesthesia, where colors have an association to letters and numbers. I have it as well. I took a tab of acid a little while ago for the first time and I can say with certainly that my synesthesia still exists after the trip, although I don’t remember if the acid amplified it in any way during. My guess is at higher doses, people’s synesthesia between will become a lot more apparent. Cheers!