Our eyes may be legacy systems, but they are really good at spotting patterns, especially things that look like they don't belong in a set.

This mixing method is another way we can simulate lighting and color found in nature. It's a bit more complicated, but my favorite way of explaining it is this: Everything outside has some "yellow" mixed in from the sunshine during the day. Same thing happens when everyone and everything looks bad in photos taken under the glow of green flourescent lights - there is green added to all of the colors you're looking at, including adding a green glow to your skin if you're standing under the flourescent light yourself. Whether it looks good or bad, this color (light) mixing creates a visual harmony. We don't really notice it when it's there, but we really notice its absence.

When you're painting, you want to simulate similar lighting conditions for a scene, and that effect is accomplished mixing a bit of one color into the other. Mixing different ratios of the same colors will usually generate a matching color palette.

How do I decide what to do? Thanks to art school and science, I know that cool colors have lower luminosity than warm colors, and will dominate in mixes, with yellow being the lightest color. For example, a touch of blue will really affect yellow, whereas you can add a lot of yellow to blue before it is affected. So, here is this decision making in function form - I am weighing different colors differently when mixing.