I see letters and numbers in colors (this is called grapheme-color synesthesia)....I also associate textures and emotions with numbers.....certain numbers are soothing to me and other a little frightening. Some numbers are soft and fuzzy like 2, 4 and 8, and others are hard and shiny like 3 and 9. The number 6 is little and dark grey, while the number 9 is huge and blood red.....my fiance's new red cabinets remind me of the color nine....blood red and so shiny I can see my reflection in them. Certain combinations of numbers are colored depending on the particular digits they contain......some numbers have a more intense color and sometimes the colors blend together like 3226 is a reddish-orange, because 3 is red, 2 is yellow (but soft and less intense than the red of the number 3), and the color of the number 6 kinda just vanishes.....
I also can easily tell if numbers are prime by the way they feel to me, and because I associate numbers with colors and textures I can easily memorize long sequences of numbers....and I'm pretty good at doing math.
Letters work in a similar way. Entire words have colors associated with them (like numbers some colors of letters are more intense and dominate the word), however I don't' associate textures or emotions with words and letters the way I do with numbers. But this also gives me a very good memory for anything I've read or written.....this made school very easy for me, more so in college and grad school.....
I didn't know this was called synesthesia until I was a teenager, I used to get in trouble when I was younger because I'd argue with a kid who made their letter P violet, when clearly it is green. Letters and numbers in the wrong colors are upsetting to me. My sister's cell phone displays all the letters and numbers in rainbow colors, but they are the wrong colors...I can't stand to look at her phone......
On first glance I usually will see letters and numbers in their appropriate colors, then as I begin to focus and concentrate the colors fade to black or blue or whatever color they actually are.