If you only intend to use the HDD for data storage, the Green drives are adequate. Though the reliability on them isn't that great, be sure to back up anything important ot another medium.
However, a 128GB M4 is not going to store a lot of games, so unless you plan to rotate games out a lot, you may want an HDD to store your games on. With how big games are getting these days, you'll probably only be able to get two major titles on your SSD at any one time. Really, you don't need to put games on an SSD, the only improvement you will see over an HDD is slightly faster startup and loading times. I run all my games off my 1TB Caviar Black and they all start and load up fairly quickly, an SSD would only shave off 1 or 2 seconds at best.
If you do want to run games or programs off your HDD in order to save space on the SSD, get the Blue or the Black. Blue is the midrange option that offers decent performance, but doesn't carry a large price premium. Black is the performance drive, as fast as you'll get on an HDD without using RAID or getting into the 10 000 RPM Velociraptors. Whether the price premium attached to the Black is worth it is up to you.