One option is to put a font selector in the options menu specifically related to texting. I don't know how difficult it would be to do this, but it is an option that I have seen in other games, and think it might just be the trick you need to increase accessibility for more people.
I know this is basically what you were alluding to with your reply, but font style selection between a few of the most common fonts along with an option to change text color itself might also make it easier for colorblind people as well. Maybe even add in the ability to make font bold or italic would increase accessibility even further.
Just my two cents on the subject.