The Sounders were unable to replicate previous dominant form over the Rapids, drawing 1-1 at home.
Colorado, looking to buck the historical trend, scored first. Drew Moor headed home Nick LaBrocca's corner on the hour mark, charging forward to the goal line after sounders backup Andrew Weber misjudged the delivery.
The lead stood for just five minutes. A Lamar Neagle shot careened off Colorado's far post and fell to DeAndre Yedlin, whose shot from middle distance was parried by goalkeeper Clint Irwin, but the young fullback followed up with a headed finish to equalize. The goal makes the 20-year-old the youngest-ever player to score for the Sounders.
Moor came up big at the other end late on, positioning himself well to head a Zach Scott header off the line.
The result puts Colorado in danger of slipping from the playoff spots if Los Angeles is able to defeat Vancouver. Seattle is now without a win in its last three matches.