Colorado (14-3, 3-1 Pac-12) won its first road game in conference play and has won seven of eight overall. Siewert hit 4 of 6 3-pointers and Bey made his only attempt from long range to give the Buffaloes some much-needed offense.
It was a disjointed, physical game that was equal parts good defense and bad shooting. Colorado finally made a few shots in a row midway though the second half and an 11-0 run pushed its lead to 44-32 with 10:35 left.
Arizona State (10-7, 1-3) has dropped five of its last seven. The Sun Devils pulled within 49-44 with about 7 minutes left but Siewert responded with his fourth 3-point to stop the rally.
Colorado's McKinley Wright made a layup with 33 seconds left before halftime to tie the game 28-all going into the break. The Buffaloes struggled on offense for much of the half, shooting just 9 of 27 (33%) from the field.
Siewert helped early by scoring 11 points off the bench in the first half, making 3 of 4 shots from 3-point range. Arizona State was led by Martin's 12 points.
The two teams already played once this year, Nov. 8 in China. The Buffaloes won 81-71 but it didn't count as a conference game.
Colorado: It wasn't the prettiest win, but the Buffaloes will take it. Colorado starts three juniors and a senior and the veteran presence was obvious when the team didn't panic after a poor offensive start.
Arizona State: The Sun Devils had a chance to win this game thanks to their defense, but the bad offensive day was too much to overcome.
Colorado: The Buffaloes travel to face Arizona on Saturday.