Let n be the total number of outfits.
n = (number of clothes)*(number of colors) = 4*3 = 12
Create a tree diagram. Pick one of the clothing (shirt, pants, socks, and hat) and one of the colors (purple, blue, and orange). You'll end up with these possible outcomes:
Purple shirt, blue shirt, orange shirt, purple pants, blue pants, orange pants, purple socks, blue socks, orange socks, purple hat, blue hat, and orange hat.
P(Orange Hat) = 1/12