How about Houttuynia cordata? I call it "hoootenanny" and some people call it a pest, but it likes moist soil, takes sun or shade, and comes in a multi-color cultivar called 'Chameleon.' A word of caution: some say it is invasive (it wasn't in my yard, but I have drier soil), so be sure it's in a place where it has room to run. You might also bury some protective edging along the perimeters to keep the rhizomes from spreading where you don't want them to.
A less invasive alternative? Carpet bugleweed, also known as Ajuga reptans). It is also available in multi-color cultivars.
Luke Miller, editor
Garden Ideas & Outdoor Living magazine