Which of the 4 banks are considered "PAIRS"?

[lighttech08]

My PC has 4 banks for memory. I am running HP Pavillion a6400f. Banks 1 & 3 are BLUE, and 2 & 4 are BLACK. According to the SPEC sheet for this MB, RAM capacity is 8 GB. Configuration says "One of the following in pairs; 512MB, 1GB, or 2GB". I have 2X1GB, and 2X2GB. Which DIMM should go in which bank to 'pair' them properly?

 

[clutchc]

Matched sizes in matched color slots.