[MudDuck]

I agree with the others saying it's coming from under the siding. Too much water pressure forcing water under the siding. Almost impossible to not do when your trying to rinse really well but still. I'd try to wash it again with light pressure with house wash recipie again, (with bleach), just enough to get it wet and dwell some. Hopfully the soap / bleach solution will break, lift, fade the red. Light rinse down, then wax additive rinse to bring out some deeper color luster of the painted board. Test first though.