Because of the nature of your project, it is actually quite easy. I have been working with electronics and microcontrollers for 15 years and have made many things like this. I would be happy to send you some pics of the various things I've made).
I would use a small microcontroller as your base (cheaper than discreet parts). This would switch between the two sides (colors). You would then simply have two light-groups, run in parallel with a resistor (probably a 220) with each. You would also need a simple transformer so you could plug it into the wall.
The schematic is easy, the PCB design is easy. I would use EAGLE for the design and GERBER files. You would need to send the PCB out for fabrication, but I know several places that will do it at a discount.
The entire thing shouldn't take more than a day or two.