Valeri opened the scoring in the 21st minute, heading a left-wing cross from Vytautas Andriuskevicius past goalkeeper Tim Howard.
Portland (11-9-7) made it 2-0 two minutes later when Darlington Nagbe received a pass from Andriuskevicius just inside the penalty area, turned and chipped a floating shot over Howard and into the top right corner for his third goal of the season.
Portland has won four of its last six to move into a tie for second place in the Western Conference with Sporting Kansas City, a point behind Seattle.
Colorado is winless in its last seven and has lost both games with interim head coach Steve Cooke in charge.
- Cup of Coffee with Cealey: Rapids ready for Portland Timbers9NEWS.com
- How Portland's back line is undermining a stellar attacking seasonFourFourTwo USA (blog)
- Timbers v. Colorado Match PreviewThe Portland Mercury (blog)
- Portland Timbers keep it close in 2-1 win over Colorado RapidsStumptown Footy
- Diego Valeri sets goal scoring record as Portland Timbers beat Colorado Rapids 2-1OregonLive.com
- Portland Timbers vs Colorado Rapids: How to Watch, Previews, Match Chat [7:30]Stumptown Footy
- Nat BorchersKPTV.com
- Game Preview & How to Watch: Portland Timbers vs. Colorado RapidsBurgundy Wave