KinderArt Littles: Blotter Bugs (Pre-K-1)
Try this color-mixing lesson for preschoolers.
http://www.kinderart.com/little28.htm

Do a Color Mixing Class Experiment (Pre-K-1)
Students form hypotheses and test them.
http://www.col-ed.org/cur/sci/sci68.txt

Color My World (Pre-K-1)
The students experiment with colors and discover which colors are created when the primary colors are mixed together.
http://www.col-ed.org/cur/sci/sci64.txt

Mouse Paint (Pre-K-1)
Connect to literature with this colorful story about three mice who discover jars of paint and learn about secondary colors when they start playing in them.
http://www.eduplace.com/tview/tviews/hoyler30.html

Childfun Colors (Pre-K-1)
This is huge collection of songs, poems, games, and general color activities. You can also select from a pull down menu and see a unit pertaining to a specific color.
http://www.childfun.com/themes/color.shtml

One Color or Two (Pre-K-1)
Students make predictions, conduct experiments, and record the results as they see individual colors separate into their components.
http://www.col-ed.org/cur/sci/sci164.txt