It is easy to have a colorful garden when you have good sun exposure. Full sun all day also creates drier conditions that can be tough on some plants. There are a number of drought-tolerant flowering perennials that thrive in this type of situation.
Lavender is a great choice for hot exposures. Not only does this plant bloom best in full sun, it requires very little water. The fragrant oils in the flower heads will be more intense if water is withheld during the mid-summer bloom period. English lavender (Lavandula angustifolia) is by far the most cold-tolerant of the lavenders. It is hardy to USDA zone 4. More tender forms like Spanish and French lavender can only be grown in USDA zone 9 or higher.
For intense color, try geum (Geum chiloense, or "Mrs. Bradshaw"). This early-season sun perennial has vivid orange-red flowers held above the plant on wiry stems. It is a good choice for adding color to the rock garden or the succulent bed. Geum is hardy to USDA zone 4.
Yarrow (Achillea millifolium) is an extremely adaptable plant. It is carefree and drought-tolerant. Yarrow comes in white, pink, red, yellow, gold and orange colors. The ferny foliage develops into a large clump, which is easily divided. The umbel like flowers bloom all summer long. Yarrow is hardy in all zones.
This plant (Agastache) is also called anise hyssop or hummingbird sage. It is not a true hyssop. If given a dry, sunny position, it will develop tall flower spikes that bloom for a long period during the summer. The flowers and leaves are both aromatic. A popular salmon variety is "apricot sunrise." Anise hyssop comes in many shades of orange. Hummingbird sage is hardy to USDA zone 5.
Though not a true fuchsia, Zauschneria is a great plant for hot sunny gardens. From late summer until frost, this plant will be covered in orange to red tubular flowers. The silvery foliage is also attractive. Once it is happy, it will spread and reseed. It is also listed as Epilobium, and both names are considered acceptable. This California native is hardy to USDA zone 5
Blanket flower (Gaillardia) is the perfect plant for those who love ray-type flowers. It is a perennial flower that blooms all summer long. The petals are usually multi-colored in shades of yellow, orange, red and brown. This plant is wider than it is tall. It is a great medium-sized filler plant placed between taller perennials. Blanket Flower is hardy in all regions.
Tick seed (Coreopsis) has been gaining in popularity. This is likely due to the many new color varieties there are to choose from. The long-time favorite "moon beam" variety blends well with other perennials due to its lemon yellow flowers. The blooms are small and plentiful all summer long. Tick seed develops into a medium-sized ferny ball of color. Other varieties are orange, red and pink. Many of the flowers have darker centers. The majority are hardy perennials, but the zones vary with each variety.