What has to be done to bring out the beautiful color of coleus leaves?
Some of my plants are really dull looking, and others are beautifully colored.
Traditionally, coleus were shade annuals. Now there are sun-loving varieties as well. Make sure that you are growing the varieties developed for the sun in the sun, and those others for shade. That can make a difference in color intensity. Color intensity can also be reduced in dry sites, since coleus prefers a moist environment.