Hi & welcome, Karen! Your gardens are magnificent!! I'm blown away!
So sorry to hear the mildew has found you. I heard about this a few yrs ago & haven't bought any new Coleus since. From what little I understand about it, it can't thrive in high temps. The links have some suggestions for treatment.
Here's some info on this awful downy mildew:
http://www.greenhousegrower.co... (worth waiting for the ad, IMVHO)
http://pnwhandbooks.org/plantd...
Some other colorful plants you might like...
Perilla
Beefsteak Plant (Perilla 'Magilla')
Perilla 'Magellanica'
Iresine herbstii (a red plant)
Bloodleaf (Iresine diffusa f. herbstii)
Hypoestes (comes in white, pink, red)
Polka Dot Plant (Hypoestes phyllostachya)
Tradescantia zebrina (purple/green/gray stripes)
Inch Plant (Tradescantia zebrina)
Tradescantia pallida (a purple plant)
Purple Heart (Tradescantia pallida)
Tradescantia spathacea (dramatic purple back of leaves, various pink stripes)
Oyster Plant (Tradescantia spathacea)
Begonias (too many to paste links to, various rhizomatous, wax, and cane types are amazingly colorful and easy to care for)
Alternanthera (various)
Joseph's Coat (Alternanthera ficoidea 'Partytime')
Calico Plant (Alternanthera dentata 'Purple Knight')
Joseph's Coat (Alternanthera littoralis)
Joseph's Coat (Alternanthera ficoidea 'Red Threads')
Alternanthera ficoidea 'Snowball'
(and many others in the plant database in search for Alternanthera.)
Breynia
Hawaiian Snowbush (Breynia disticha)
Euphorbia tithymaloides (dramatic pink highlights)
Variegated Devil's Backbone (Euphorbia tithymaloides 'Variegata')
Bromeliads & earth stars (too many colorful/variegated ones to link)
Aglaonema (Chinese evergreen, many colorful cultivars)
Gynura (a fuzzy purple plant)
Purple Velvet Plant (Gynura aurantiaca 'Purple Passion')
Plectranthus (various variegated ones)
Variegated Cuban Oregano (Coleus amboinicus 'Variegatus')
Plectranthus (Plectranthus discolor 'Green & Gold')
Plectranthus (Plectranthus forsteri)
Stromanthe
Stromanthe (Stromanthe thalia 'Triostar')
Codiaeum (Croton)
Croton (Codiaeum variegatum)
Cordyline (Ti plant)
Ti Plant (Cordyline fruticosa) (look at individual cultivars too)
