I have honestly no idea, but I do know that I don't break word or numbers into different colored parts (excepting typology systems), so I think it's just because they are getting higher.
Interesting, I break down them into parts instead. (Words into letters, numbers into digits and they have the same colours as single digits or letters)
I think the first letter might be a bit more noticeable (stronger colour) than the rest. It may be the reason why I only remember the first letter of words. I'm otherwise really bad at recalling words or text word by word.
Oh and I recall something else now. I used to have a period where I made up some "magic sentences"*, they were just sentences with everyday words otherwise**, and somehow I involuntarily associated colours with the sentences. The entire sentence would be one specific colour. And yeah it was consistent too but it was a long time ago (I was like 13-16-ish so over 10 years ago) and I stopped using the sentences and I don't remember them anymore.
*: sorry long story as to what that means
**: meaning was special though, used them as a kind of control over my own mind, as I said long story!!
That's pretty cool. It sucks that Synesthesia can be comorbid (even though it isn't a disorder) with mental deficits
As far as I know, I don't have mental deficits. Quite the opposite, my brain is well put together, thank-you

Even if it has some special wiring
Perhaps one thing though, I don't have much focus on theory of mind stuff. I'm able to do basic ToM instinctively no problem but the more complex shit I just don't pay attention to.
Ohh well and another thing, something is off with my sensory processing of movement but it doesn't often cause a problem, it's a small side thing. (It's like, processing of motion and other visual information together under certain circumstances will get messed up; my brain will start to go to "sleep"; I have to find a reference point to resolve it but that is okay then. This happens maybe once in every few years lol, the circumstances are pretty special ones)
Which reminds me, has every person with Synesthesia been left handed at one point or another?
When I was younger (before like 3rd grade), I was predominantly lefty, but then I just changed for some reason.
No but I can use my left hand as much as my right hand if I want to / if willing to practice
Have you ever experienced Sound to Sight projection (not even color projection)? It's really fucking scary and I don't get it often. If I am in a state of deep concentration and mental fortitude, then I can see what appears to be static behind everything, and it can overwhelm my vision, but it never completely closes out the visual world. It's almost mesmerizing.
Can you say more about what you mean by the bolded? I didn't understand that at all. Thanks.