A bishop's skullcap, also called a zucchetto or pileolus, is violet. The double-pointed hat worn in procession, called the mitre, can be many different colors, but is usually a plain white linen with...
Generally white, but it can be the color of the liturgical season or celebration ( red, violet, or green)
Violet is the color worn by bishops.
Red is worn at Confirmation - the color symbolic of the Holy Spirit.
The color of their attire varies according to what particular Feast Day is being celebrated.