Not all the time, but with some letter, numbers, or words i will think of a color. Certain letters remind me of colors and when I see them I can't stop thinking about the color. For example, in math we were using the variables "ay" and for some reason it reminded me of a bright red. And the number 4 makes me think of yellow. I don't know why my mind is thinking like this. Is it normal?

Read the book. It's about a girl with synesthesia and how she had to deal with it. Although not all people with synesthesia pair the exact same things.
I think about sounds in terms of shapes and images all the time. Also, I tend to associate feelings with certain colors and landscapes.
Completely normal. Just another quirk of the human mind. :)
1: Maroon
2: Navy Blue
3: Yellow-Orange
4: Dark Blue
5: Brown
6: Burgundy
7: Red
8: Yellow-White
9: Dark Green
Sunday: Light Pink
Monday: Pink
Tuesday: Dark Blue
Wednesday: Red
Thursday: Brown
Friday: Dark Brown
Saturday: Navy Blue
A: Dark Blue
B: Light Blue
C: Blue-Purple
D: Yellow-Orange
E: Maroon
F: Dark Brown
G: Pink
H: Yellow
I: Off-White
J: Burgundy
K: Brown
L: Dark Green
M: Dark Red
N: Light Brown
O: Very Dark Brown
P: Navy Blue
Q: Very Dark Purple
R: Green
S: Red
T: Brown
U: Very Dark Green
V: Brown-Purple
W: Orange
X: Very Dark Grey
Y: Yellow-White
Z: Dark Red