Colored water includes water colored with food coloring as well as water containing dyes. Because of the way plants interact with dyed and colored water, the colored and dyed water has a wide range of applications from coloring cloth to floral applications and herbicidal control.
One science experiment that elementary school teachers use to show students how plants absorb water is to place a cut flower into water that has been colored with dye, which will change the color of a flower's petals along the margins and veins. A dye placed in water will change a flower with white petals to the same color as the water. Flowers that have pigmentation in them may be changed into a different color as the dyes in the water respond to the pigmentation in the flower's petals. For example, a yellow daffodil placed in blue water may have its petals turn green due to a mixing of the colors.
Aquatic plants need sunlight and oxygen to thrive just as plants on land do. But when a pond is filled with dye from pollution or wastewater runoff, the dyes in the water will reduce the amount of light that can penetrate to the deepest parts of lakes and rivers. This lack of sunlight penetration can kill the plants in a lake or pond. In some plants, the zone of water that light can penetrate is so thin that all but the shallowest parts of the water body are devoid of plant life. In some bodies of water, dyes may be applied for algae control. These bodies of water should never be used as a source of drinking water.
Natural dyes are dyes that are obtained from the pigments found in many plants. Examples of natural dyes include yellow that comes from yellow onionskin, red-brown from henna and dark blue that comes from the indigo plant. Natural dyes are not as color fast as synthetic dyes. These dyes do not absorb into cloth made from plants such as flax, cotton or hemp as well as synthetic dyes. Hair and cloth made from hair such as wool absorb natural dyes more readily than plant fabrics will.