EDIT: Also, the descriptions people report of their imagination when reading a narrative description or exposition of a scene often include details seemingly arising in a loose associative way from the words themselves, without being explicitly described in the text.

EDIT 2: And I'm not entirely comfortable with the notion that people experience the world in a "fundamentally different way" when there is evidence that this may not be a fundamental difference after all. Different it is, no doubt, but this seems to be a difference of magnitude rather than fundamental nature. The predominant character of the experiences may be subjectively different, leading to a different approach to many situations in a person's life, but the mechanisms appear to be fundamental to consciousness itself.

An upside of synaesthesia is that I have very good clerical accuracy, which is helpful for programming—typographical errors “stick out” because things appear the wrong colour. A downside is that I can’t really use syntax highlighting, because I find it distracting. This is what my terminal Emacs looks like: https://imgur.com/m76W8eF (with soft wrapping because there’s not really a line length limit in this codebase).

I didn't think about this, but does feeling a smell or scent in different emotional strengths also count to synaesthesia?

I guess I should stress that I don't "see" these colors. I just know, intuitively, that they are there. They are the color of the letters in my mind's eye, if you will. I suspect thus that it has nothing to do with the shape of the letters, but is a side effect of how my brain processes the language, and understands the underlying phonemes. That would also explain why the vowels seem to be so much brighter, since they are the most important letters when I'm scanning text quickly for comprehension.