"The voters have spoken, and we have to respect their will,"Colorado Governor John Hickenlooper said after Tuesday's voting.
"This will be a complicated process, but we intend to follow through. That said, federal law still says marijuana is an illegal drug, so don't break out the Cheetos too quickly."
Amendment 64 legalized marijuana for anyone over 21. It is to be sold at state-licensed stores that would pay taxes that were expected to generate millions of dollars in revenue for the state government.
A similar measure to legalize the recreational use of marijuana failed to pass in neighbouring Oregon.
Those results were among the most closely watched initiatives on the ballot while in another major issue, voters in Florida rejected a measure that would have severely limited the reach of President Barack Obama's health care reforms.
Measures in California that would ban the death penalty and raise taxes to solve the state's chronic budget problems were well behind in vote tallies with about 20 per cent of the ballots counted.//DPA