There is some overlap between the Colorado and the H3, mostly the I-5 block and 4l60e transmission. The intake on the H3 was modified to be lower (to clear the lower hood height), the differentials on the H3 are Cast Iron (on newer models) vs Cast Aluminum, forged control arms instead of stamped, full-time 4wd transfer case in H3 v 2wd/4wd selectable in the colorado, lower gear ratio in the H3 (I think 64:1 in the I-5 version). I think the Z71 Colorado has more in common with the H3, but not 100% sure about that. I don't believe you can get lockers in the Colorado/Canyon.
TXH3T - your truck is looking awesome! Makes me want to get rid of my H3 and switch to a truck. You are doing a great job representing the brand and using your truck for exactly what it was designed for!