Guard Rex Pflueger notched 14 points and 10 rebounds to record his first career double-double for the Fighting Irish. Guard Matt Farrell scored 12 points and matched a team high with five assists.
Notre Dame (2-0) improved to 18-0 in home-opening games under coach Mike Brey since 2000-01.
Mount St. Mary's (0-2) fell to 1-29 all time against ranked opponents. The Mountaineers trailed by single digits late in the first half but were outscored 48-30 after the break.
Guard Junior Robinson scored 14 points and had three assists to lead Mount St. Mary's. Forward Bobby Planutis contributed 11 points and grabbed seven rebounds.
Notre Dame shot 52.4 percent (33 of 63) from the field and 33.3 percent (4 of 12) from 3-point range. Mount St. Mary's shot 39.3 percent (24 of 61) from the field and 31.4 percent (11 of 35) from deep.
The Fighting Irish pulled away with a 14-0 run to start the second half. Farrell assisted on a layup to Colson and drilled a 3-pointer on the next possession to punctuate the outburst.
Mount St. Mary's scoring drought spanned 4:07 before Planutis made a 3-pointer to cut the deficit to 54-35. The Mountaineers trailed by double digits the rest of the way.
Notre Dame established a 40-32 lead at halftime.
In the final moments of the first half, Colson hit a step-back jump shot to put his team up by eight. Colson confidently put his head down and jogged toward the locker room after beating the buzzer.
NOTES: Notre Dame G Matt Farrell increased his 3-point streak to 28 consecutive games when he drilled a shot from beyond the arc in the first half. ... Mount St. Mary players attempted 3-pointers on five of their first six shots. ... Notre Dame coach Mike Brey moved within 10 victories of becoming the school's all-time winningest coach. Brey (384 career wins) trails only Digger Phelps (393) on the list.