4 RAM Slots-2 sets of dual channel...Am I capable of running..........?

I just got a new mobo and never had 4 RAM slots before on a Micro ATX board. there are 2 sets of dual channel RAM slots, 2 of which are red and the other 2 are yellow. Because they are both dual channel does that mean that I can run 8 gigs (4 x 2 gigs) of RAM with each dual channel mode using different speeds of RAM? I know that one dual channel mode must use identical RAM even down to the name brand of the RAM, but can I run 1 dual channel mode with 1066 ddr2 RAM and the other with 667 ddr2? each is 2 x 2 gigs, but just different name brands and speed, or do I need to run 4 sticks of the exact same RAM? it supports up to 16 gigs, but I have a new set of 2x2 ram in my current computer and a set of 2x2 from an older computer. will it run each dual channel mode independently of each other ultimately giving me 8 gigs of RAM, or do I have a wasted set of $120 RAM? my original intention was just to use the old set as a back up set, but I realized that I have 4 slots that are 2 dual channel slot modes. Thanks for the answers!!