Alrighty, sorry I just got home from work so wasn't able to reply until now. Warning this is gonna be a long read. This is what you asked for so you gotta earn it by reading this wall of text. Muahahaha!
When combining colors to obtain new hues, there are three basic colors that cannot be made by mixing others together. Known as primary colors, these are red, blue, and yellow.
If you combine two primary colors, you create something called a secondary color. For example, mixing red and blue produces purple; yellow and red makes orange; blue and yellow combined make green; red and blue make purple. The exact tint or shade of the secondary color you create depends on which red, blue, or yellow you use (light or dark), and the proportions used. If you mix three primary colors, you get black.
When combining colors, remember that it requires only a small amount of a dark color to change a light color, but it needs a lot more of a light color to change a dark one. So, always add dark (eg. blue) to light (eg. white), not vice versa.
Similar to the situation when mixing dark and light, remember that only a small amount of opaque color is needed to change a transparent one. So make a point of adding opaque to transparent, not vice versa.
So this is really basic. The point is you can control shifts a number of ways. You can build up light to dark layers and minimize your shift. Or you can take a lot more time and mask it off to protect it.
Understanding the theory of colors is applicable to anything airbrush, or anything art for that matter. Without fundamentals of color theory and art, while anyone can airbrush, it's a whole lot easier and faster if you get them now before you venture too far and get frustrated and quit this medium. Art is basic principles mixed with a ton of trial and error. Learning from mistakes makes you better. I still make mistakes. Everyone does. Mike lavalle, Mitch, and any other pro makes mistakes, they just understand theory and can apply it to make the mistake never happen, or at least make it appear that way.
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