I don't think I have synthesia but when I wonder about it I get something like this:
A, B, C, E, F, I, J, K, O, Q, T, U, X, Y, 1, 3, 4, 5, 6, 7 Female
D, G, H, L, M, N, P, R, S, V, W, Z, 2, 8, 9, 0 Male
My favorite letters are E and R:
E - yellow (almost orange), female, tolerant, smart, clear
R - dark red, male, expressive, confident, bossy, sharp
They make a great team together. E makes R less sharp.
My least favorite letters are O and L:
O - pinkish brown, female, huge, plain, boring, slime
L - greenish brown, male, rude, swallow, tasteless, sharp
Seeing them together makes me uncomfortable. As looking at something ugly.
My favorite numbers are 4 and 7:
7 similar to E but lighter color, the same shade of yellow/orange but ligher.
4 similar to R but female and more vivid red
Together they make a fun pair, like 2 smiling girls on a playground.
My least favorite numbers are 1 and 2.
The pair (female and male, white and blue) are selfish, adults, rule bound, rough
They are like a pair of police officers or something.