Don't be afraid of the darks
Black paint - a lot of artists say it's a no no, but I find it crucial to the success of my rainy-day paintings.
Most of us have heard it .." don't use black, it will make your painting look dead". Then we are told the best and darkest darks are those made up of other colours. For rainy-day city scenes there is nothing nicer that using black, but in conjuction with other colours. The blue/purple darks are suitable for sunny days but don't always work for the rain. As we know, with atmospheric perspective things tend to blue off as they recede into the distance. However on a rainy day it is more likely that things will grey off. The blue darks just don't look right. Experiment with black and mix with other colours like yellow ochre, raw sienna, ultramarine and reds. A multitude of warm and cool greys await you and make for great paintings.