Think of how you apply the meaning of color day to day. Color is something that surrounds us and has since the beginning of time. Color effects our perception and even our mood. Color also holds unfathomable depths of symbolism.
One thing that we apply color symbolism to but should not, is actually magic itself. The two most common forms of "color magic" are the ideas of "white" and "black" magic. White magic generally considered good is the opposite of black magic, which is of course bad. However, the symbolism usually applied to these colors does NOT apply here because the good or evil of magic is determined by the individual, general purpose, and final outcome. In either form of these two magics, the final outcome can have unforseen results that go against the general symbolism of whichever type you have used.
There still remains plenty of room for color symbolism in magic, despite its common misuse. The planets in the Milky Way Galaxy show one use of proper color symbolism. Proper color symbolism is used when a color, though it may have various meanings, is generally accecpted by the majority (EXAMPLE: Color= Red- Life bc of our blood, anger, and passion). Probably that largest factor in proper use is that whatever purpose you are using a color for is set in its meaning for your goal and the meaning cannot become the opposite bc oif the purpose of your color changes, then so does your goal.
In conclusion, I actually managed to only scratch the surface of the different ideas behind color. I would actually suggest to further research colors independantly. As you further your understanding in this area, do not forget what you have read here.
I believe there are colors simply for the fact that black and white show us what it looks like for the perfection of all colors combined, and the utter absence of color for black. But is your argument based on more of an idea that there are colors b/c that is just what our mind perceives? Let me know.
another point on white and black magick is that they are not so as commonly held diametricaly opposite for example a friend contracts the swine flu you as a magician and healer natural performs a spell to heal your friend an act kindness so at this point a act of white magick but what about the virus is this not a natural occuring living organism innocently doing what what nature intended it to do so now you are harming a living thing remember the harm none rule so now faced with inaction and allowing your friend to suffer for you to choose to act now the underlying ethics have changed the spell is now for your benefit and so to ease your mind the magician has now become a sorcerer and this in turn makes the magick for personnel gain and now it has become black magick for the start points are the same but the intent changes and the end result totally different