I always shoot black and white in my M3. Except that is, until I ran out of film last week and had to use an emergency colour one lurking in the bottom of my bag ...... yep, you guessed it! A whole roll of variously coloured shots, dependent on the filter on the lens in use........
*slaps head, while muttering "D'oh!"
I've been shooting a looooooooooooong time and still make silly mistakes