Answer:
There are 36 ways in which he can wear combinations with three items of the different color.
Explanation:
Hat Pants Shirts Shoes
red black red black
blue blue black red
green green white blue
white white
If we look carefully we see that he can choose any hat, any pant and any shirt but he can choose only one pair of shoes that does not match with any of the three.
3C1*4C1*3C1*4C4= 3*4*3* 1= 36
There are 36 ways in which he can wear combinations with three items of the different color.