My dreams, at least all that I remember, have been in color. They look no different than a TV screen, all colors being about equal.
That said, if a color really stands out, I have always assumed it to mean 'pay extra attention to this object/character.' One dream in particular had many colorful antique cars in it, all had been restored to pristine condition, and all were used in an every day manner. The cars, more than the people who drove them, were a key element in the dream.