I have nowhere near the experience many of the Guys/Gals on this forum do........I pretty much just shoot B&W Film.
BUT.....I usually bring along my Canon Sure Shot 80 tele...and I keep THAT loaded with Color Film. Just a habit I got into when the Sure Shot was new. Seems like by the time I pull 36 frames of B&W, I always find a need for a few frames of color.
The Sure Shot is so small and light (compared to my F2 and A-1).....it is a real joy to have handy.
Mine still seems to keep up steam, but I would love to be able buy a brand new one.....
good luck