It is Common Sense not Permutaions nor Combinations!

Question is here!

You need only 3 attempts.

Let's say on first draw we get BLACK socks. In next draw, if we get BLACK then we have matching pair immediately. But if in second draw, it's WHITE then we have to go for third draw. 

On a third draw, if it's BLACK then we have pair of BLACK socks ; one came from first draw & other from third one!

On the other hand, if we get WHITE on third draw then we have pair of WHITE socks ; one we got from second & other from third.

Same logic can be applied if WHITE comes in first draw.