They should rotate at the same speed front to rear whether a locker is used or not. The transfer case splits the power 50/50 front to rear so everything should be equal.
Not all 4wd trucks have a locking differential. It's a feature typically reserved for more off-road orientated vehicles. That being said, the Colorados did have a G80 rear locker offered on certain models. The G80 locker engages when it detects a difference in the passenger/driver wheel speed.
I personally don't care for the G80 locker design and removed it from my rear axle and replaced it with a selectable locker. A front locker from a Hummer H3 can be installed in a 1st Gen front differential but they weren't an option on any 1st Gen Colorado. I installed one a few years ago and it worked well until I did my SAS.