Prothane makes bushings in both colors. But is there a difference in them? Is one harder than the other? There are a lot of misconceptions about the color difference in Prothane's bushings, so let us at DST clear that up for you.
Aside from the actual color, there isn't really a difference at all between the red and the black. They are the same durometer, or hardness, so they will perform the same and both should last the life of your vehicle.
The black bushings do have a small amount of graphite mixed in with the polyurethane which has the potential to help with squeaking. But really, the best way to prevent Prothane bushings from squeaking is to use the supplied pre-lube* and grease them properly at install. So whether you choose the red, or the black, just be sure to grease them properly to avoid any squeaking.
* Some types of bushings only compress, such as body mounts and endlinks, and do not come with grease because they do not need grease. So if your kit comes with grease, be sure to use it!