Here is an article I wrote about color mixing . . . enjoy!
In the world of color theory there are three main, or primary, colors. These primary colors are red, yellow, and blue. It should be possible to create all other colors with just these three colors, in theory anyway.
In reality, you need a few more. . .
Anyone who has ever visited an art supply store or the paint aisle of a craft store knows that there are many versions of 'red, 'yellow', and 'blue'. How do you know which one to use and what do all those names mean? If I'm painting water do I need ultramarine? What the heck is alizarin, cadmium, and dioxazine? They sound more like chemicals than paint colors!
I've experimented with this for years, a little obsessively, in the quest to simplify my paint collection. After reading everything I could from the experts and doing some experimentation on my own, I have come up with nine colors that can handle almost anything you want to paint. The key is to select two of each primary colors. That's right, two reds, two yellows, and two blues. Why? Because of a little thing called color bias. (I know, I know, how can colors be bias? It's ridiculous, right?)
This idea of color bias leads us to color temperature.
All reds and yellows are warm and all blues are cool, right? Not so fast . . . we can actually find both cool and warm colors in each primary: red, yellow, and blue. How can you tell? Honestly, this can get a little tricky – which is why I'm writing this post. Let's start with yellows. I bet if you walked into a paint store you could find some yellows that were closer to green (cool) and some yellows that are closer to orange (warm), right? That, in a nutshell is color bias. Lets try the same with red. Could you think of a red that is closer to orange (warm) and a red that is closer to purple (cool)? Finally, blue. Imagine a blue that is closer to purple (warm) and a blue that is closer to green (cool). That's it! You've got it! If not, don't worry. It takes practice. Why not visit an art supply store and try this exercise in person? You could even do it with paint chips in a hardware store or Walmart!
Here is what the warm and cool primaries look like in reality:
But this is only six colors, remember I said I use nine to create almost any color I need?
(I actually should have said ten – I forgot white!)
I discovered that there were some greens and purples that were not as vibrant as I would like – so I added a green and purple to my palette and that took care of that and I got some awesome black replacements to boot! I also added neutral gray so I could mix subtle transition colors found in the landscape. And last but certainly not least (it's used in almost all mixes) you need Titanium White.
Here is a demonstration of how color bias/temperature can affect your color mixes. Lets say you want to mix a bright green. You know that yellow + blue = green. Easy, right? Let's see what happens when you mix a warm yellow (Yellow Oxide) AND a warm blue (Ultramarine Blue)
Definitely not the green you are looking for!
Maybe a cool yellow (Cadmium Yellow Light) and a warm blue ( Ultramarine Blue)?
But can you get an even brighter green just using yellow and blue? How about a cool version of each? YES!
Mixing a warm yellow with the cool blue still gives you a pretty nice, although muted, green. This color would be very useful in landscape painting.