Coreopsis. One of the easiest-care perennials. Long bloomer, starting up in summer and continuing through autumn. Daisylike flowers bloom in bright yellow, but there are also varieties with golden yellow, pale yellow, pink, or bicolor blooms. Deadhead flowers to encourage additional bloom. Zones: 3-9.
My 2nd favorite perennial ever. I've had the same one at my folks house for 7 years and she does NOT have a green thumb. Blooms from May til Halloween, no joke! This is Early Sunrise Coreopsis. The more sun, the better! Zone 3-9
Heuchera, Electra (Coral Bell) Electric red veining remains unchanged while foliage transforms from bright green/yellow in spring to chartreuse in summer, soft red in fall. Short spikes of white flowers, 8-12 " height
Creeping Jenny, Golden Moneywort. (Lysimachia nummularia Aurea) Excellent, fast spreading groundcover forms a leafy mat only 3” tall. Foliage will be bright yellow in full sun. Penny-sized gold leaves freely root at the nodes. Profuse buttercup yellow flowers in summer. Provides a perfect blanket of color beneath Hydrangea, Hostas and Ferns. 3" Height.