SB 113, which would repeal the Colorado magazine ban, was just passed in the Colorado Senate.
The bill passed by 20-13 vote and was just sent to the Colorado House. If the bill is passed by the house and signed by the governor, the Colorado magazine ban prohibiting ownership of magazines capable of holding more than 15 rounds of ammunition would be repealed.
Unfortunately, this is an uphill battle. While Republicans control the Colorado Senate, the House is controlled by the Democratic Party and Governor Jay Hickenlooper (also a Democrat) was the same guy who originally signed the controversial gun control bill containing the magazine ban into law back in 2013.
Though passing SB 113 is going to be a tough fight, it's not impossible. If you're a resident of Colorado, contact your representatives in the Colorado General Assembly, as well as the Governor, and let them know you support SB 113 and want the Colorado magazine ban repealed.
You can read the full text of SB 113 here. However, the two main points in the bill are that the bill repeals provisions prohibiting the possession of large-capacity ammunition magazines and requiring each large-capacity magazine that is manufactured in Colorado on or after July 1, 2013, to include a permanent stamp or marking indicating that the magazine was manufactured or assembled after July 1, 2013.