TRACER is the Colorado Secretary of State's Campaign Finance system.

https://tracer.sos.colorado.gov/PublicSite/Homepage.aspx

For FEDERAL races (US Senate and US House of Representatives) go to the FEC site:

Click for US SENATE - COLORADO

Click for US HOUSE of REPRESENTATIVES - COLORADO

(You can also filter by District and/or Party using the "Candidates" tab in the left column.)