So, I saw your post about tetrachromacy and am wondering if I have tetrachromacy because the letter O to me is scarlet but not really scarlet! I've never actually seen the color O is, or D or 9 or Q or most other letters! Confused!
Many synesthetes have talked about how a letter is a colour, or combo of colours that doesn’t exist in real life. (Like, for me, N is both peach and lavender mixed together but not mixed at all.)
The fact that you haven’t actually seen it confirms that you do not have tetrachromomacy. I’m not sure what you would call tetrachromocay that only exists in your mind/mind’s eye.
Sorry, I’m don’t know a lot about tetrachromacy, any one else have more details?