This year, I'm taking an advanced level art class in school! I am learning a lot and really enjoying myself, so I decided to share what I've learned to help others and help me remember in the future.

Most of this was taken from the color lesson I was given because I thought it was pretty cool.

Supplies

Some sort of palette. I used wax paper because it works, but paper plates, palette paper, cardboard, most disposable surfaces work.
Thick paper. I recommend white or neutral grey.
A palette knife - I used a paintbrush instead, but you should really use a palette knife. They're much better. I just happen to be a broke student who doesn't own one.
A paper towel or two
A container full of water
Red paint - I suggest Cadmium Red Medium Hue
Blue paint - I suggest Ultramarine Blue
Yellow paint - I suggest Cadmium Yellow Medium Hue
White paint - I like Unbleached Titanium

This tutorial involves acrylic paint, but you can use the concepts in here for pretty much any paint. Color theory can be used with any medium, so it's very useful to learn for any reason.

Step 1: Vocab Terms

In order to understand this Instructable, you'll have to understand these following terms:

Primary Colors - Red, Yellow, and Blue. These are the purest colors that are not made out of other colors. They are the base for every color out there.
Secondary Colors - Orange, Purple, Green. Combinations of two primary colors, no more no less.
Tertiary Colors - Mixtures of all three primaries. These are what the majority of the world's colors are made up of, and what any realistic painting would use.
Shade - Making a color darker
Tint - Making a color lighter
Complementary Colors - Colors that when mixed, cancel each other out. The mixing of all 3 primary colors makes gray, a color's complementary color is whatever colors are needed to make that gray. So green needs red to have all three primary colors, so green and red are complementary colors. Yellow need blue and red to have all three primaries, and purple is composed of blue and red, so they are complementary colors.

Step 2: Preparing Your Color Chart

I used a light pencil to sketch the chart shown above on my paper.

The triangle connects the three primary colors, yellow, blue, and red. The colors across from each other, connected by a line, are complementary. The smaller circles are shades and tints of the base color in the larger circle.

Step 3: Measuring Your Paint

Squeeze out a pea-sized amount of red, blue, and yellow paint to use for painting the circles. Be careful when squeezing it, making sure to squeeze slowly from the bottom to prevent the paint from splattering. (I did not do a good job of this.)

Generally, when mixing paint, it's better to make too much than too little so that the shades match throughout the painting. However, since the areas being painted here are so small, we can get away with small amounts of paint.

Step 4: Paint!

Fill in each of the circles connected by the triangle with a different primary color. You do not need to be neat, as this chart is just for reference. I like to try to put a thick layer of paint on so that the color is more saturated.

Between colors, make sure to wash your brush off! Aggressively swish it around it water to help get the paint off, and then dry off the water on the paper towel.

Step 5: Mixing Orange

Pour out a small amount of yellow paint, and then add red a little bit at a time until you get orange. You want to start with yellow because it is less pigmented than red, so a little bit of red had a stronger effect than a little bit of yellow.

Mix it with a paintbrush or palette knife, depending on what you have. Then paint it onto the circle between red and yellow, as shown in the photograph.

Step 6: Mixing Yellow-orange and Red-orange

To mix yellow-orange, combine some yellow with the orange you have already mixed. You should end up with a shade somewhere between yellow and orange. Make sure to still leave some orange for red-orange. Paint your color onto the paper between yellow and orange.

Mix a very small amount of red with the orange to make red-orange. Paint it between - you guessed it - red and orange. Make sure to still leave some orange paint for the tinting and shading.

Step 7: Repeat for Green

Just as how you made orange, make green! Green is composed of yellow and blue, so starting with yellow, mix in blue until you get a satisfactory green shade. Add more yellow and blue for the yellow-green and blue-green, keeping some green for tinting and shading.

Step 8: Mixing Purple

See if you can apply the concepts used before to mix purple, red-purple, and blue-purple!

Step 9: Shading With a Primary Base

In order to shade a color, you should add its complementary color to it. In the case of red, that is green. Add a very small amount of green to the red until you get a darker red, and add it to the chart below the red.

As said before, complementary colors contain the hues needed to make a grey color. If you are unsure what a complementary color is, just think - what is this color missing from the 3 primaries?

Note: you can also use black to shade, but that often comes off as too harsh. Using complementary colors is a better way to gradually shade something, it also comes off as more natural because most often, pain fresh out of a package is very saturated and not very realistic.

Step 10: Tinting

Since white is less pigmented than the darker red you just made, you start with the white and add the red into it. Mix it up like you would any other paint until you get a light red color. Then paint it onto your chart below the dark red.

Step 11: Repeat for Green

Green is made up of blue and yellow, which means it is missing red. Add a small about of red to the green to darken it, then add some of that paint to white, making sure to add the colors to the chart.

Step 12: Shade and Tint All Primary and Secondary Colors.

Using what you have learned before, create the shades and tints for blue, orange, yellow, and purple and add them to your chart.

Step 13: Paint! (Or Do Something Else)

Your chart should look like the image above. If not, ask questions!

Now that you have at least a basic grasp of how to mix colors, you can start making some pretty cool paintings and such!

Some fun ideas for painting practice:

Use complementary colors in an abstract painting
Paint some fruit. I like clementines.
Try mixing shades to match random things around you like the wall closest to you, someone's hair, wood, anything that looks cool!