Dd does this and I did, too. We agree on some but not all. I figured it might come from posters in our classrooms or favorite books etc that imprinted a color on a number or letter, or common examples of them (T is green, perhaps because they always show turtles in our abc books... And it starts the word three, which is also green!). But maybe it is some synesthesia.

My mide DDs letter/colour pairings are clearly from learning the alphabet playing on Starfall, her colours are a perfect match for Starfall.

DH told me he has always seen music as colors and patterns. I will have to ask ODS.

My DD9 has recently told me that sometimes she is distracted by the arguments that the numbers have with one another. Apparently the number 7 is particularly pouty. This has been going on for years but she has only mentioned it recently. Have any others here experienced/encountered anything similar?

Numbers definitely have characters. 7 is the privileged big sister, 5 is cool, 2 is like a big happy dog or smart-enough jock, 4 is friendly, 6 is the number I identified with...

This is me too. Also people's voices are colours. The narrator of the YouTube vid that my son is currently watching is blue with smears of brown. It's a youngish (20 something) voice so in places the blue is thin, like water colour, but it's a little deep, so that's where the brown blending comes in.

FWIW, I read a book on synesthesia years ago, and I don't think I have it. For me it's more like a processing thing - like a visual representation of sound. I think true synesthesia is more striking and vivid (for lack of a better description).

Found it!

http://www.amazon.com/The-Tasted-Shapes-Bradford-Books/dp/0262532557

"The ten people in one million who are synesthetes are born into a world where one sensation (such as sound) conjures up one or more others (such as taste or color)."

Good book.

Not to digress too much, but aquinas mentioned something I just heard about on NPR: autonomous sensory meridian response. ASMR is a real thing, different people have different triggers, which for you are perfect fifths and octaves.

DS15 has talked about synesthesia for years, I didn't know about the cuisine ire, etc. Now I'll have to review his connections with him to see what it is! And BTW, I used to think I had it, but was probably influenced by my obsession with color-by-number sets when I was a kid.

The book _A Mango Shaped Space_ by Wendy Mass is about a child with synesthesia. Might be interesting for your DC to check out.