Boyd gave Killie the lead after 48 minutes before the striker was red carded on the hour mark, with Danny Lennon's side then drawing level through former Kilmarnock player Gary Harkins.
The home side began brightly, with Kilmarnock goalkeeper Craig Samson doing well to keep out Steven Thompson's downward header.
Killie began to work their way into the contest, Boyd flicking the ball onto Paul Heffernan but his shot from six yards was blocked by goalkeeper David Cornell.
Heffernan again went close just before the break, the striker curling a shot towards the corner of the goal that Cornell did well to push round the post.
The away side began to look more threatening after the break, with Rabiu Ibrahim causing problems for the St Mirren defence.
The Nigerian set up Kyle Jacobs for a shot that went straight at the keeper before he played his part in the Kilmarnock goal three minutes into the second half.
Ibrahim sent Seann Clohessy down the right flank and his cross was met by Boyd six yards out, the striker finishing neatly.
Referee John Beaton then turned down a penalty appeal from St Mirren after Paul McGowan went down in the area before Boyd saw red.
The former Rangers striker was dismissed for an off-the-ball incident as he inexplicably punched defender Jim Goodwin.
St Mirren soon took advantage as Harkins created a yard of space inside the box to score from close range on 64 after Kilmarnock had failed to clear a Danny Grainger corner.
The Buddies almost grabbed a winner as their opponents held back but Gary Teale's cutback evaded three team-mates inside the area as they secured their first point of the season.