Actually, my understanding is that Colorado Republicans will have a voice. There is no straw election for a presidential candidate at this year's caucuses because of the rule that states that for any caucus held before March 15th the delegates MUST vote in the 1st election at the primaries for the candidate selected in the caucus. By not voting in the caucus for a candidate, it allows the Colorado delegates to vote for any candidate at the primaries in the 1st election instead of potentially being tied to a candidate that may have already dropped out prior to the primary.
Example if we selected a candidate at the caucus:
"Candidate A" is selected in the caucus.
"Candidate A" drops out of the election prior to the primaries.
Colorado's delegates would still be bound to vote for "Candidate A", which would basically equate to not voting because the candidate is no longer running.
By not selecting a candidate, this is avoided and the delegates can vote for the candidate that most represents what the voters they represent want.