(Source of image: www.sanford-artedventures.com)

       The six colors can be painted in a circle, or wheel.
It's called a color wheel.
Each color has a certain place on the wheel, depending on how it is mixed.
 

First you can fill in the three primary colors YELLOW RED & BLUE
Next you can place the three secondary colors ORANGE GREEN & PURPLE in between the two primary colors that are mixed to create that color. Green sits between blue and yellow on the color wheel because it is made up of these two colors.  Orange sits between red and yellow.
And the color purple sits between blue and red.
 
 

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(Source of images: www.sanford-artedventures.com)
 
 

Did you know that colors have a temperature?
They can be warm or cool.
Depending on which colors you choose,
your picture will seem warm and exciting or cool and peaceful.
 

WARM COLORS
       Let's take a closer look at the color wheel.
         RED, ORANGE and YELLOW sit next to each other.
These three colors are called WARM colors.
Think of the color of the bright yellow-orange sun
and of a red-hot fire.
This is how you can remember which colors are warm.
Warm colors are exciting!
If you paint with warm colors, your picture will make people want to jump up and dance.

COOL COLORS
       Now look at the other half of the wheel.
You'll see that BLUE, GREEN and PURPLE sit next to each other.  These colors are called COOL colors.
Think of a green hillside, a blue lake,
and a purple mountain.  Cool colors are peaceful.
If you paint a picture using cool colors, it will make people feel calm and relaxed.

(source of above information and images: http:members.aol.com/Sabbeth/Colordec.html)