I was wondering what was up with this ballot measure since I saw someone collecting signatures for "open primaries". We already have open primaries in Colorado.

What it really calls for is
Establish top-four open primary elections and ranked-choice voting for U.S. Senate, U.S. House of Representatives, governor, attorney general, secretary of state, treasurer, Colorado University board of regents, state board of education, and state legislature
Ranked choice voting -- that's what they really want. This is how Alaska ended up sending a Democrat to DC. They know the majority oppose most of their extreme agenda but if they can get that majority to divide up into factions, their loons can win by plurality.

For what it's worth, I dislike open primaries even though I'm independent and do use the primaries to attempt triage (I voted for Obama in the 2008 primaries because he was less despicable than HRC). Parties should get to choose their candidates and I think if I want to have a voice in their selection, I should suck it up and register for that party.