I can see two ways to look at this. First think about drawing the socks, one after the other.
Select the first sock. What remains in the box? What is the probability that, on your second draw, you select a sock of the same colour as on your first draw?
What about drawing them at the same time.
Suppose the white socks are labeled W1 and W2 and the blue socks are labeled B1 and B2. How many ways are there of selecting 2 socks from the 4 socks? Write them down; W1,W2; W1, B1: ···
How many of these possibilities are two socks of the same colour?
I hope this helps,