Euphorbia
Euphorbias are worth pursuing for their dramatic variety. Some are tender perennials, such as the poinsettia, but others are cold-hardy. Consider Euphorbia polychroma ‘Bonfire’, with its ever-changing display of deep purple, red, and orange leaves (and a touch of chartreuse) that turn burgundy and then red from summer into fall. 18 inches tall, 36 inches wide; Zones 5 to 9. 

Hosta
Because hostas have leaves that come in an enormous range of greens, blues, yellows, and whites, they’re the go-to foliage plant for shade. Consider ‘Stained Glass’ with bright yellow leaves and an irregular dark green margin (15 inches tall, 48 inches wide), and ‘First Frost’, with blue leaves and ivory margins that turn pure white if grown in half a day of bright light (16 inches tall, 36 inches wide). The American Hosta Society selected them as Hostas of the Year in 2006 and 2010, respectively. Zones 3 to 9. 

Heucheras (also known as coral bells) come in an astonishing range of colors, from the red fall color of ‘Autumn Leaves’ (8 inches tall) to the gold-with-red-veined leaves of ‘Electra’ (8 inches wide) and the cool chartreuse of ‘Citronelle’ (12 inches tall). They send up slim stalks adorned with tiny blooms. Some, such as ‘Rave On’, produce enough flowers to make a good show, but the leaves are the real reason to grow heucheras. Zones 4 to 9.

Sedum
Some sedums perform best in sun, and others do well in shade. Their fleshy leaves help them tolerate drought, and many have leaves that look great all the time. Check out a variegated variety such as ‘Tricolor’ (Zones 4 to 9), with green leaves edged in white and pink blush in cooler weather (6 inches tall), or one with burgundy leaves that are almost black, such as ‘Black Jack’ (24 inches tall and wide) or ‘Purple Emperor’ (16 inches tall); both are hardy in Zones 3 to 9.