Houttuynia cordata 'Chameleon'
The foliage is a very important part of a garden design. Most people when thinking of colour think of the flowers. With an exception of annuals, most plants have a period of flowering after which they look a bit dull or even unattractive.
Pale flowers can be highlighted with a purple leaved plants like e.g. Ipomena batata. I use for containers.
Beautifully variegated leaves of Heliopsis helianthoides 'Loraine Sunshine'
Spotted leaves of Pulmonaria
When talking about the foliage, we must not forget the texture. Colour is always attractive but different shapes of the leaves may be attractive as well. I love ferns for their foliage feathery texture. They are good for shade, under the trees and shrubs.