Dreams in color are almost certainly gifts from God. When we discuss color it is important to keep in mind that God is a Creator, while our adversary the devil is simply a counterfeiter and corrupter. 1 John 1:5 clarifies that God is not only love, He is also light. Science is clear that all color comes from light and therefore all color comes from God. The devil, as a counterfeiter is never quite able to introduce vivid color into your dream life and therefore most dreams in black & white or muted color come from our adversary. While this cannot be held as a universal truth - due to the fact that dreamers can not always be counted on to remember the color of their dreams accurately - it can be quite helpful in determining the source of a particular dream.
Colors, like most other dream symbols can have either a positive or a negative meaning. Context and discernment are the primary means by which an interpreter can distinguish wither the elements meaning is one or the other. While the meaning of colors are not as consistent as the meaning of numbers, they do tend to have a more limited range of possible meanings. This is due to the fact that many times colors take their meaning from Biblical context or from recurring spiritual themes. On the other hand colors can also take their meaning from common usage and colloquialisms.
Consider the following examples:
Color Positive Meaning/Source Negative Meaning/Source
Red Wisdom/Scripture Anger/Colloquialism; Stop/Common Use
Blue Revelation/Spiritual Theme Depression/Colloquialism
In these examples the meaning of the color originates from different understandings, but regardless of the source of inspiration the meanings are equally valid. In the case of the color red, Proverbs 8:11 and Job 28:18 raise the idea that wisdom is more valuable than rubies (which are red in color); being red in the face is a common colloquial expression used to describe anger and the most common color of a Stop Sign in western culture is red. The color blue is repeatedly seen as a color associated with revelation in various spiritual contexts, but as used in a colloquial phrase to be "blue" means to be down or depressed.