Alright Tip Of My Tongue, got a tough one: there was a book read to me in like 3rd grade about a multi colored mountain (or possibly snow)

It was an adventure book and I barely remember it, but the visuals in it have stayed in my head from then until now (24)

Anyway I think it was about a boy and a girl who had to go up this mountain for some reason.

So that's about all I remember. It was set in like a more fantasy atmosphere or olden atmosphere rather than modern day.

My Google skills have come up with nothing and I've not remembered much except that a cape might have been involved though I don't know if that was significant or not.

Thanks for your help! I tried asking Askreddit but I was downvoted.