This author is pretty weird. Heroines should always have pink hair and a blue/white outfit? Why pink of all colors? It's pretty much one of the most ridiculous colors out there for hairstyles, barely any authors use it nowadays. It was popular earlier on, with works like to love ru. Perhaps that's where he picked up that habit. Still, to be so attached to it seems a bit silly to me, isn't it funnier to try different types? Sounds a bit boring to me if you do the same thing all the time.
Well, my color scheme for dresses for protagonists would probably be a black/gold/red combo, depending on if it's a type who fits in that color or not. Otherwise things like a white/light blue would be pretty nice for more innocent ones with a light personality or if they're creatures such as elves, a kind of light green with some white would be nice. At the end of the day, it all depends on if the character fits in the clothes. The clothes would do best to fit the personality and style, right?

As for hair color, that also pretty much depends on what they fit with. Going for only one type is kinda weird. I think that Noah would be even cuter if she had a pure white or silver hair color, that'd be much nicer than a weird pink and it'd match her eyes.
By the way, Riff would've never made a good protagonist in anything. Her personality and style SCREAMS of "side-character", an unimportant one at that. As for noah being determined and frank... Well, I don't really feel like that would suit this type of story, but that could also be nice depending on how it's done. By the way, wasn't she supposed to have SILVER eyes in the descriptions but her eyes are clearly a varying shade of blue? It goes from kinda dark to quite light in the illustrations, only in a few of them can her eyes truly be seen as something close to silver as they get to a really pale shade of blue.