There are deposits of copper metal all across Canada (Yellowknife, Coppermine, YT)
That copper was traded at least as far south as near the American Border ( lat 49N in Saskatchewan)
Some of the copper corrosion compounds are a pale sky blue which was mixed with salmon egg or oolican fish oil as binder.
Together with ochre, charcoal and ash, these gave the Haida and others on the Pacific Northwest 4 colors for illustration.
I suspect that there was some effort to use burnt clays as well.
What you see in the old things is red, black and white (sound familiar?)
TeeDee, unlike your place, there really are no habitable caves in the PacNW.
Here in BC, I can't name more caves than the fingers on one hand.
Color was used to decorate totem poles, story poles and mortuary poles outdoors.
Then masks, boxes and screens indoors.