In exchange for the 34-year-old U.S. national team player, the Galaxy will receive three second-round draft picks from the Rapids.
It was a trade neither the Galaxy nor Fraser wanted, but one that was forced by the league's salary cap.
"He's somebody who has been a valuable member of our team and somebody we hate to lose," Galaxy Coach Sigi Schmid said Sunday. "He's going to leave a hole for us in the back because we don't have a defender with similar speed."
Under Fraser's captaincy, the Galaxy defense has been ranked first or second in the league in each of the last four seasons and the team twice reached the MLS championship game during Fraser's five years in Los Angeles.
The Jamaican-born defender is fourth all-time among Galaxy players in games played (129), games started (127) and minutes (11,207).
"He was a vital part of our defense," Schmid said. "There is no defender in the league who has the combination of Robin's speed and positional sense. The only player who comes close is [U.S. national team and Washington D.C. United defender] Eddie Pope, and his positional sense isn't quite as good."
Reached at home in Pasadena on Sunday, Fraser said he was very disappointed.
"At this point, I'm drained," he said. "The whole process has drained me. It's been two months of being in limbo [since first being told in January that he might be traded]."
Schmid said the team did everything it could to keep Fraser.
"The reason it went as long as it did is because we tried to explore every option that would make it possible for us not to have to do this," he said.
The league, however, declined to allow the Galaxy any relief under the salary cap, which the team exceeded once Cobi Jones signed a new contract.
The league was willing to let the Galaxy trade a future draft pick for cap room, but that only would have been a temporary solution, Schmid said.
"We still would have to get rid of a player next year and we would have lost our No. 1 draft choice, so then we were really starting to mortgage the future," he said.
"There really weren't a lot of players we could trade for. Rather than take somebody else's also-ran, I felt I'd rather start with somebody new."
One of the three second-round picks the Galaxy is to receive will become a first-round pick depending on how many games Fraser plays for the Rapids this season.
"If you pay attention, you can find somebody good there [in the second round]," Schmid said, pointing to the drafting of Brian Ching this spring.
At least Fraser was able to go to a city he knows.
"The team of his choice was Colorado," Schmid said. "We had a couple of other [better] offers, but I felt, if we had to trade him, if we could send him to the city he wanted to go to that was something we owed him."
Fraser lived in Denver before the launch of MLS in 1996 and led the Colorado Foxes to two A-League championships. His wife, Ashley, is from Colorado.
"I'm sad because I don't want to leave L.A.," Fraser said. "I'm not happy to be leaving, but if I have to leave then Colorado's the place I'd want to go to."
Fraser's departure leaves the Galaxy with only three of its original players: Jones, Greg Vanney and Mauricio Cienfuegos.
"I've been here since the beginning and I've seen us trade away so many good players that this is just another Galaxy trade that I don't agree with," Fraser said.
The fact that a player of his stature is being traded for nothing more than future draft picks does not concern Fraser.
"I don't really feel slighted about that," he said. "I feel slighted that if we have a salary cap issue then I'm the player he [Schmid] thought should go.
"But I guess your opinion of your value is not necessarily the same as what other people believe your value is.
"I always thought I was realistic, so that's what is disappointing."