btw, there should be the ability to paint the same brick with two colors, like a double wall.
Sounds a bit awkward.
Would it be a specific brick that does this? In which case you'd need to double all default bricks in order to have this function on everything useful.
Would you have to paint either side one at a time? If you want bricks to be coloured in whole, then it would be so annoying to have to go and paint it twice.
How would you choose which colour (or side) to paint a brick while it's being placed. If I set my colour to Green, and place a brick, is the whole thing Green, or just one side, and if so, what colour is the other side?
Ignoring whatever problems there may be in it actually being coded for, I think it just overcomplicates what should be an easy process.
Why not just build your external walls one brick more outwards and then build a differently coloured interior wall?