We used 2 L-brackets per attachment point (2 or 3 points on each bumper). There were holes drilled through the outward part of the L-brackets as well as through our robot's frame. To attach the bumpers, they were placed on the frame and then pins (
basically these) were placed through the holes so that the pin went in the top bracket, through the frame, and out the bottom bracket.
For color of bumpers, we attached snap buttons to the bumper and to our blue fabric, which allowed us to go from blue to red almost instantly with one person per bumper (red to blue was obviously harder).
This system allowed us to switch from red to blue in < 3 minutes with a 4 person crew. Took one person to remove each bumper (we had 4), then each person could attach the blue fabric, then it would take 2 people to put each bumper back on (one pushing it in, the other placing the pins).
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