McKinley Wright IV scored 16 points, Namon Wright had 14 points and freshman D'Shawn Schwartz had a career-high 10 for the Buffaloes (10-6, 2-2), who built a 20-point lead in the first half on coach Tad Boyle's 55th birthday.
Center Deandre Ayton scored 26 points and forward Dusan Ristic had 13 points and 11 rebounds for the Wildcats (12-4, 2-1), who had a nine-game winning streak broken. Rawle Alkins had 16 points.
The Wildcats never led, but shaved a 20-point deficit to four on Ayton's layup with 10:05 remaining that made it 54-50.
Colorado gradually regained control, and Collier's 3-pointer with 4:35 made it 68-58 lead.
Ayton hit a 3-pointer and a jumper in the final 17 seconds, the last with seven-tenths of a second remaining, but the Buffaloes successfully inbounded the ball to end the game.
Collier had 10 points in the second half after scoring 11 points in a 90-81 overtime victory over No. 4 Arizona State on Thursday.
Walton made all seven of his field goal attempts and Collier was 5 of 7 with two 3-pointers as the Buffaloes shot 54.7 percent from the field.
Colorado recorded back-to-back wins over ranked teams for the first time since joining the Pac-12. It had one such streak while in the Big 12.
Arizona shot only 38.4 percent and was 7 of 25 on 3-pointers.
Guard Allzono Trier, the Wildcats' leading scorer at 20.3 points a game, had eight points on 3-of-9 shooting.
Walton had seven points including his only 3-pointer when Colorado went on a 12-1 run for a 23-12 lead. He had a dunk and two layups on another spurt that pushed the Buffaloes to a 37-20 lead with 5:41 remaining in the half.
Arizona called three timeouts in a 4:54 span but could not slow the Buffaloes, who had a 45-29 lead at half. The Buffs shot 64.3 percent in the first half and Arizona shot 30.0 percent.
The Wildcats opened the second half on a 17-4 run to tighten the game.
--Field Level Media
Arizona | Colorado | |
DeAndre Ayton 26 | Scoring | McKinley Wright IV 16 |
Parker Jackson-Cartwright 8 | Assists | McKinley Wright IV 10 |
Dusan Ristic 11 | Rebounds | George King 11 |
DeAndre Ayton 3 | Free Throws Made | McKinley Wright IV 6 |
Parker Jackson-Cartwright 4 | Steals | Lucas Siewert 1 |
DeAndre Ayton 2 | Blocks | Dallas Walton 2 |