Synesthesia is when two senses combine with each other and form relationships. For example, I have the most common kind: grapheme-color synesthesia. Mine looks like this. The only one that’s supposed to be black is “1”. Otherwise, the ones in black have no color associated with them.
Yeah, mine helps me, too! I use colored markers on the back of my cards when I need to remember the pin numbers. Since I have a horrible memory due to ADHD, depression, and anxiety, this is pretty much a life saver. Especially since my numbers all have unique colors. I’ve contemplated making my own font where each letter is just a square that’s colored, but letters like M, D, and B might get mixed up. I’d have to almost “refine” their colors if I want to be able to tell them apart. I was also pretty good at spelling. :) Maybe this thing is a mini superpower. lol