Just an article I found interesting in ND Magazine and thought I'd share - one for the Landscape photographers!
http://nd-magazine.com/photography-in-bad-light/

I have certainly found that sometimes, even in bad-ish light situations that certain colour can be drawn out as a contrast to gloomy days you just have to wait for the right moment, such as when the sun peeps out from behind a cloud and gives that lovely contrasty, rich colour:

IMG_0525 by Adam Brice, on Flickr