The depiction of a battle with the sioux in 1797 painted on a mandan robe (3.4.20) was created using

The depiction of the battle of Sioux in 1797 on a Mandan robe is made using a buffalo robe. This buffalo robe is a cured buffalo hide with the hair still left on. The paint used on the buffalo hide are made from natural pigments. The hide is tanned and painted afterwards.

answer; the masks were used in rituals and celebrations, some tribes wore animal masks as a way of thinking the animals for their gift of food;

yellow and blue because thats what i remember, im not sure tho