Experiments that illuminate the color spectrum are not only enriching but can be dazzling if displayed in a science fair. A range of science fair projects deals with how colors fade and why, with a variety of materials and themes. Pick one appropriate for your topic, age level and means, then craft it meticulously to woo the judges.

The dyes used in fabric can fade for many reasons. A science fair project that could interest anyone who wants to keep their clothes looking new would show how a variety of factors affect the coloring of different types of fabric used in clothes. Cut several squares of unwashed fabrics, such as denim, cotton and polyester. Place one set in a dark controlled environment and expose the rest to a variety of environments for a predetermined period of time: hot washing, cold washing, bleaching, direct ultraviolet light outside and/or under a UV lamp. Chronicle your results and compare how these treatments affect the color-fastness of each swatch.

Younger students can explore whether colors fade at different rates if they're made of the same materials. Hypothesize, before you begin, whether colors will fade at equal or unequal rates. One week before the fair project is due, fill four cups with water and a drop of food coloring, one color per cup. Stir each. At a set time every day, check the color for fading and take a photo while keeping the temperature constant. Make note of when you start seeing the colors noticeably fade. See if any color fades faster than another. Avoid yellow as it can be difficult to determine when it has faded.

Colors can fade for a variety of reasons, such as when perceived by the eyes in different ways. In a Fading Dot experiment, you can make the colors on a dot fade when viewed through an optical illusion. Cut out a blue circle, 1 inch in diameter, then glue it to a pink piece of paper. Cover the pink sheet with wax paper and look at the dot. Slowly lift the wax paper from the pink paper to see how the blue dot changes. Look immediately to an area at the left or right of the dot and the dot will disappear because of the subtle twitching of your eye.

If you can plan far ahead, an experiment with different colors of soda cans over seven months can illustrate how ultraviolet light from the sun can make dyes fade from even metal surfaces. Set the cans together in a spot that gets an equal amount of sunlight every day, such as a windowsill. Monitor and photograph the changes that occur every month and use a diorama to show the results.