If you know how to do it so you don't have to redo it all. Maybe add a way to allow players to change font color through settings.
FYI you can change the text box opacity already, that may help. Changing font and box color afaik requires a different version of rpgmaker, but that version is laggier on some devices.
That I didn't know. I didn't see that option in the settings. I only saw default settings.