Dye/paint Blocks

What if using a cauldron with dyed water in it you could use a brush to add a colour on it and you could paint/dye one side of a block. e.g if your building a house and you want the inside a different colour but you dont want to make it 2 blocks thick so it makes the windows or doors look strange, you could have the outside the colour you want and on the inside using a dyed brush you could paint that one side of the block to the colour you want. This feature could work with any coloured block like concrete or wool and would enable the community to add more to their builds.