They are intended to make it easier to determine if your netbook can handle a game at a glance. In case you're unsure of what some information means, I've explained it all below.
Don't know which platform your netbook is built on? All you need to know is which GPU you have.
GMA 950 = Diamondville
GMA 3150 = Pineview
GMA 36x0 = Cedar Trail
Radeon HD 62x0/72x0 = Ontario
Radeon HD 63x0/73x0 = Zacate
ION & ION 2: self-explanatory
It's easy enough to tell the difference between red and green, but what about the different shades, and what do they mean?
Red - You can't play the game on this platform.
Orange - There's a chance you can play the game with some overclocking (mainly on Diamondville netbooks); in the case of Cedar Trail, it means the hardware is theoretically capable of playing the game, but is being held back by Intel's atrocious driver.
Yellow - Cedar Trail only. It means the game will theoretically work, but hasn't been tested.
Light Green - With exceptions, the platform can handle the game well. These exceptions are specified in the Notes.
Green - Think of this as a 'Gaming with Netbooks Seal of Approval'. The game will run on all processor/graphics configurations in that platform (with enough RAM, that is). For Cedar Trail, it means the game has been tested and runs with a satisfactory framerate.
I've only prepared tables for games that only work on more powerful netbooks. In other words, if a featured game is headed by 'Recommended: Depends', then there'll be a table. Games with 'Recommended: YES' or 'NO' don't need one, for obvious reasons. Games like StarCraft 2 that fall under the questionable category will be explained with text, rather than a table.