Chlorophyll

• Chlorophyll, the green pigment, is present in all plants. Chlorophyll is produced through photosynthesis, the process by which plants transform sunlight into food. When deciduous plant leaves change in the fall and winter, losing their green color, it's because the plant has stopped producing chlorophyll. Plants go dormant, losing all their foliage, when they stop creating chlorophyll and photosynthesizing. Chlorophyll is responsible for green leaves and flower petals.
  
  

Carotenoids

• Carotenoids are the yellow and orange pigments found in flowers. The name hints at the colors carotenoids create; it's responsible for the orange found in carrots. Carotenoids create the yellow and orange tones found in sunflowers, marigolds, buttercups, tiger lilies and many other flowers and plants. Carotenoids form in plants and flowers during the growing season.
  
  

Flavonoids

• Flavonoids are responsible for the widest range of colors in flowers. Flavonoid pigments are responsible for blue through red flower shades -- all reds, pinks, purples and blues. Freesia, gladiolus, roses, iris, orchids, lavender and many other flowers gain color through flavonoid pigments.
  
  

Color Changes

• Flower colors serve a function in nature by drawing the attention of pollinating insects. Flowers need bees and other insects to spread pollen from flower to flower, which makes it possible for the plant to produce seeds. But flower colors do not always stay the same. Some flowers change colors after they have been pollinated, or once they've aged past the point of pollination. Lungwords, delphinium and forget-me-nots change from blue to pink.