Clean Drones are an attempt made by Sentai scientist at recreating the original drones, however developing them so that they would not revolt. This was the result.
The Clean Drones are created with limited AI capabilities - the only features they have are basic language and the ability to learn. With this, they are brought up as one of the scientist's "children", learning skills as they go much like a human being. When they reach the age of 5 months, they will have learned enough to start in the wide world (these guys/gals learn quickly). They are trained along with human recruits, and eventually joined into the Sentai Provence Army, where they progress up the ranks along with the other humans. They are treated as a human at all times.
The colours on the back of their heads and chests indicate rank/learning level: red is the basic stage, blue is recruit/Sentai Provence Troop, and green is Sentai Provence general.
This is an interesting concept, though given the fighting the drones, I doubt many humans would trust them. The SPA looks very suspiciously at Mecha Nine when he defects, and he and his forces are almost single handedly responisible for saving the tattered occupation force survivors, sent to reclaim the Urban Sector from the Drones, after General Seino's death at the hands of Mecha One. But I do like the idea, this seems more likely to fit before the Robot Rebellion. But that is my opinion. ^Blub^