It is impossible to very dramatically shut the person out of our thoughts and feelings. Just because the relationship ends, does not mean that all is finished. Either way, dreaming about your ex-romance does not predict future involvement. It may be wish fulfillment, reliving memories, or working out old issues. Dreams are very rarely prophetic.
Colors are symbolic.
Blue - some believe that it is a very spiritual color and that when you see it in your dreams you may be in the presence of your spiritual guide. Otherwise it may symbolize positive thinking and optimism about the future. Green - can have several different types of meanings depending on the details in the dream. It could represent money, jealousy, concerns about health, or love. Red - passion, anger, or a warning.