seems to me the girls are already color coded. (size chart)
=> red, pink, green, blue, yellow, purple
probably easier to use as 'anonymized' placeholders
Personally I actually prefer the characters having predefined names. I'm reading a story about those characters and it allows for contextualized usage of the names. like wordplays or with the older succubus explaining the meaning of "red" and "pink"'s names which is giving us more context about that succubus character.
Thechnically it should be pretty easy to implement. It is just a variable declaration/ usage like with the MC-name.
for the text/dialogue its a simple find and replace.
If the names bother you, you could probably even do it yourself.
It looks like a pretty simple/standard renpy project. Just decompile it, run the find and replace with your prefererd names and run the game from the renpy sdk or compile it again. whatever floats you boat.
(you'd have to do it for every new release though)