I would say look at at the Colorado Parks and Wildlife website to start with. They have a lot of good info. Also GoHunt is great for helping pick units. Gohunt and OnX are two resources I utilize heavily, also Google earth.
Cory Jacobsen has a great video for E scouting using GE after you've picked a unit. I used his methods last year in Montana and had 4 good encounters in a week in a challenging unit.
I am from Tennessee planning my second elk hunt. First one to Colorado and I am a research and planning junkie. But I will say, the eastern portion of the state is mostly private and has a smaller elk herd I believe. I would say you need to at least get west of I-25.
Some Westerners probably know better than I, but that is my understanding.