memory - Is this the correct way to slot in RAM and is the number okay?

I was using a 2GB DDR3 ram stick on my last Computer, I got a new motherboard which had an offer for 4GB so I took it, got home and discovered it was actually 8 GB DDR3 RAM, two identical 4GB sticks. Pretty cool. :P

Anyway, The motherboard has four slots, two blue and two black. They are arranged like this:

Blue | Black | Blue | Black

I have placed the two 4 GB sticks in the blue slots, and the spare 2GB i had in a black slot. It's probably overkill, but might as well use it I figured.

Is this the correct way to arrange them? Would the 2GB hurt performance, with how channels work?

Thanks.

edit - motherboard is a ASUS M5A 78L-M USB3