In the give cubes, which colour is opposite to purple?

From the given cube positions:

1st cube: Purple is adjacent to Blue and Red.
3rd cube: Purple is adjacent to Red and Green.
4th cube: Purple is adjacent to Green and Orange.

So, the four colours adjacent to Purple are:
Blue, Red, Green, and Orange.

A cube face has exactly 4 adjacent faces and 1 opposite face.
Therefore, the only remaining colour opposite to Purple is Yellow.

Final Answer: (c) Yellow