If you’ve got blues and greens, or whatever, growing on your home’s roof and outer walls, here’s what to do. Roof mold discolors shingles -- especially lighter ones. It’s mostly found in damp climates on north-facing roofs and on heavily shaded walls where surfaces stay damp enough to promote mold, fungus and even moss. Often simply trimming back nearby trees and bushes to reduce shade and improve air circulation eliminates the problem. Roofing dealers also sell zinc-coated strips that fasten near the ridge, and oxidize when it rains, inhibiting mold and fungus. When it’s time to re-roof, buy mold-inhibiting shingles. For mildew on outside walls, use bleach and warm water -- instead of expensive commercial cleaners. Got a green substance taking over your home? Fight back with sunshine, fresh air, water and bleach and simple mold- and fungus inhibitors. And that's the On The House tip for today.