There was a sky blue also that was popular...even white/multi-colored striped or green/ black striped. I have a reference where there is a painting of a chief in an all black one with red piping...very impressive.
The Hudson Bay Company capotes can give you a range of colors that blanket coats were made from during that period.
As Enion wrote, it would be wool. Most Great Lakes tribes were into heavy decoration and beautiful beadwork also.
You have a lot of leeway with this garment's coloring...and almost anything would be correct.
I do have a book about Great Lakes Indian Clothing, and evidently they did use a hide version (probably deer or elk) that followed the HB pattern...so if you used your buckskin painting talents, you would be correct also.