The color of a plant's flowers attracts your eyes as well as pollinating insects. Color also helps with plant identification. The flower color, however, may change in response to stress, temperature, soil minerals and plant age. In addition, the perception of color varies based on light conditions and the observer's gender. "Men tend to see primary colors such as blue or green, women (see) more distinctions such as turquoise or chartreuse," according to Dr. Leonard P. Perry of the University of Vermont.
Plants show color in flowers, berries and leaves. A flower's primary colors are an easily observable characteristic to begin the process of identification. A common terminology for plant identification uses the names of the colors on a color wheel. Primary colors are red, blue and yellow; secondary colors are green, orange and purple. Tertiary colors are named by combining touching segments on the color wheel, such as yellow-green and red-orange. A color-based plant-identification guide also includes color-wheel colors mixed with white, creating lavender, pink and gold.
Other colors on plants are less visually dominant than the primary color, but they may be essential in making a correct identification. For example, tansy asters, daisies and blanket flowers all have similar yellow petals. However, the secondary colors on the interior of the flower are yellow, black or red, depending on which plant you are viewing.
The color on a flowering plant may be solid or may have variations in intensity or distribution. Plant-identification guides use descriptions of color distribution such as variegated, striped or spotted. The distribution of primary and secondary colors may be explicit, using a description such as "yellow flowers with a dark red center," or implicit, with terms such as "gradually shading from light to dark."
Shape and Size
Second in importance to color for plant identification are the size, shape, number and arrangement of petals on the flowers. Flowers may have distinct petals or have one petal that is lobed on the edges. The petals may be of equal length or lopsided. Petals may flow out from a defined center or be clustered.
To identify a plant based on color, describe the plant in detail in a notebook or on index cards. Measure the size of the flower and its components and the height of the plant. Note the conditions at the time of your observation, such as the location, time of day and season of the year. Also note any conditions that might affect plant color, such as moisture, disease or soil. Take a picture of the plant--including the flowers, leafs or berries--and annotate the picture with your description. Compare your sample with pictures and descriptions in plant-identification reference materials.