Organizing a plant identification guide by flower color makes a lot of sense. Flowers are often the most noticeable part of the plant and are often the reason a plant is added to a garden.
Botanists categorize and identify plants based on flower structure. How many petals are there? Are the flowers held singly or in a cluster? Flower color usually has a minor, often no, role in plant categorization and identification because there are problems using flower color for these tasks.
Flower color can vary between plants of the same species because of growing conditions, plant age, or just from natural variability. Some flowers change colors as they age. The flowers of spreading fleabane, for example, are pink in bud, white when first open, then turn lavender as they age. Often all three colors are present at the same time. Solving this problem of multiple flower colors by listing the plant under all three colors runs the risk of creating a system that provides little help when trying to identify the plant.
Added to this is the variability in how humans see color. One person may judge a flower as pink; another as purple. One person sees white; another pale blue.
To identify your plant by flower color, select from the list below. Note that bicolor flowers are classified under the flower color they appear to be from a distance. Grasses are classified separately, with no attempt to sort by flower color. Cactus are classified by both flower color and as a separate category.
Plants with white or cream flowers
White flowers can sometimes appear light blue, purple, or pink. If you don't find your plant here, try those colors as well.
Plants with yellow flowers
Yellow flowers are perhaps the easiest to sort by color. You may see flowers you would classify as "gold", a color which can grade into orange.
Plants with red or orange flowers
Red or orange flowers are often clearly those colors, but sometimes you see a color in between and sometimes orange flowers will have red markings and vice versa. Deep pink flowers may appear red.
Plants with pink flowers
Pale pink flowers can sometimes be judged as white. Pink flowers may also be seen as purple or lavender and photographs may not record these colors accurately. If you think your flower is pink, check the blue and purple flowers also.
Plants with blue or purple flowers
Pale blue and purple flowers can sometimes be judged as white. Purple/lavender flowers may be seen as pink and photographs may not record these colors accurately. If you think your flower is purple, check the pink flowers also.
Cactus
Grasses