BOULDER — The University of Colorado opened Pac-12 play Saturday night against No. 7 Washington with the program’s most football season tickets sold since 2012. CU had sold 20,785 as of kickoff, an increase of 2,774 season tickets from last fall. From 1990 to 2012, the Buffaloes hadn’t dipped below the 20,000 mark, but the 2017 total is just the third time since 2010 that CU has broken the threshold. Colorado State, on a bye this week, had sold 15,507 season tickets this week in the inaugural season with its new on-campus stadium.