Chevrolet 2010 Colorado Owner's Manual page 312

How to Check Lubricant
To get an accurate reading, the vehicle should be on a
level surface.
A. Drain Plug
B. Filler Plug
6-46
If the level is below the bottom of the filler plug hole,
located on the transfer case, you'll need to add
some lubricant. Remove the plug and add enough
lubricant to raise the level to the bottom of the filler
plug hole. Use care not to overtighten the plug.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See Recommended Fluids
and Lubricants on page 7-10.