2000 GMC S15 ABS

I recently replaced front brake pads, rear pads, front rotors, right front abs sensor, but for some reason when I brake and the vehical is coming almost to a stop the ABS wants to activate. I bled brakes (i didnt flush) I noticed brake fliud coming from rear was some what greenish but no air in the lines. The ABS light is not on nor does it flash or go on when this happens. The light does go on if I unplug either of the front sensors. And of course if I unplug either of the front sensors (wich turns off the ABS ) it does eliminate the problem. But thats not the fix I want.(This problem started before I replaced anything, the brakes were worn I was hopeing it would fix the ABS problem after I finished the repairs.