All natural (mostly) wood stains! A handful of pennies in vinegar will produce a beautiful pale Caribbean blue stain. A wad of steel wool will give you a rich reddish hue. A combination of tea and a metal object in vinegar will produce a black stain.
When you paint a room, put some extra paint in a baby jar* and keep it handy for quick touch-ups. don't use a baby food jar - use a peanut butter jar that has a PLASTIC lid or it will rust - shake well and use a q-tip for quick touch ups.