Normally I'd be all about colouring if I was using SAI :B
But right now I'm messing around on clip studio paint and colouring is kinda hard for me D; Can't flip back to SAI since it's not mac compatible...sigh.
I think they look far better as is than they would if colo(u)red. The style is far more interesting as is, but no, I don't think they are unique enough/detailed enough to be worth real money. And just saying imho from the samples you have given the girl looks far better than the boy, as the artistic use of the stripes seems lost and overall boring in the latter.