I tend to agree that B&W on overcast days makes for some wicked looking shots. I have managed a few good ones in colour on overcast days....but it does really depend on the conditions and how you expose the shot.
This one for example was shot late afternoon, the orange glow being the sunset (off to my right) with the storm clouds rolling out to sea.
IMO this had to be a colour shot, because of the orange glow.