I'd say you use MokyjeBrutes idea if you use a special e.g. green texture for the selected entity.
Or if you want to preserve the textures appearance without having a light and normal version of every entity-texture in game you as well could attach a shader to the selected object if your A7 version supports it.

them draw them like toons! hehe

heh.. its really simple :))
no shaders, no problems.. this take me about 2 minutes to get it work correct

Glad to see it works now ^^