If we subtract green from cyan, we get
Red
Blue
Yellow
Magenta
Combination of green and blue gives us cyan. Hence on subtracting green from cyan we will get blue.
The elements of sets A , B and C are all colours as follows:
A = { Red , Orange , Yellow , Brown } ,
B = { Blue , Yellow , Green , Brown } ,
C = { Black , Brown , White , Grey }
Then, A U B U C is