Lug pattern is 6x5.5" or 6x139.7mm, you need a hub bore diameter larger than 100.1mm, and for offset it depends on what you're doing, how wide the wheels are and how much you plan on dropping it. For a 20x8.5 a +25mm or higher is recommended if you plan on dropping a lot, you can get away with something like a +15 or +18 but they'll be even with the fenders or stick out a little bit depending on if you have flares and what kind of flares.
Look for my thread on the American Racing Trench in this forum. They're offered in an all black 20x8.5 +30 offset specifically for the Colorado/H3/Canyon.