The weather on any given day provides the color palette for a photo. If there isn't enough color or too much color I might choose to process in b&w. There's a certain kind of light on a rainy day that is quite nice. Photography is a process for me which always holds a bit of surprise. When I see the photos I will decide how they should be processed. I like both b&w and color though I definitely lean towards having a better appreciation for black and white photography. Regardless, rain and umbrellas are fabulous for photography.