"Can Colorado really achieve 100 percent green energy by 2040?"

Yes, we can, but not the way we're going about it.  We already have two cost-effective renewable energy technologies:  nuclear, and hydroelectric, but the environmental extremists put up roadblocks against both, in favor the the crony-capitalist solar, wind, ethanol, and bio-fuel lobbies who lobby for tax subsidies in exchange for campaign donations and votes.

We should take a look across the pond at France's nuclear energy program that provides 70% of the electricity without, apparently, a spent fuel storage problem because they continuously recycle and reuse their spent fuel, but for mysterious reasons, we don't.

We need a lot more dams to capitalize on our snowmelt.  We need the water and the hydro-electric power that should be generated from it.  If an occasional rodent gets displace, he'll adapt. The best fly-fishing is in dam tailwaters.