Some will color faster than others. I kept mine in brackish water, though, so I don't know that it will make a difference. My males started showing black at 3 weeks and real colors at 4 weeks. My females got some black and yellow at about 25 days, call it 3.5 weeks. I did end up with a couple of "false" females, which were actually males that developed an obvious gonopodium at 4 weeks before they developed any color at all.I know about the water quality I issues, I bought them before learning about that.
There is absolutely no aggression in my tank, the betta is super chill so it won't be a problem.
It sounds like it's sort of a mystery as to what color they will be so we will see!
How long until they color up?
I kept mine in brackish water to get around my hardness issues.
As long as you are aware of possible issues, I won't badger you about it.