Ok so basically me and my friend are building my school on Java. There is a wall that in the inside is painted white but the outside of the wall is just bricks. How do I make the inside of the building white and keep the outside brick without having a 2 block thick wall. Thanks in advance
Maybe hang banners outside? That's the only vanilla thing I can think of that might work. There isn't a way to paint blocks in vanilla, although it's possible plugins, mods or command block stuff that is beyond me could hold the answer, but that's only speculation.
Maps in item frames would do it though it would take 256 stacks of white blocks to get an all white map of the smallest size, or find a large expanse of snow, then there'd be less that had to be filled in manually.
Well, he did specify a way to do it without making the walls 2 blocks thick, although I do agree that would be the easiest way.
Hexalobular mentioning maps made me remember a plugin my server has if you're playing on a server. it's called artmap or something. Search it up, I don't know much about it because I don't use it, but it might be the answer you're looking it
Chisels n Bits and Little Tiles let you create custom blocks using whatever materials you have handy. You can do some amazingly-detailed stuff with it, all within the space of a single block.
OpenBlocks, and various other mods (pretty much all of which add in a whole lot of other things that are useful or OP across the entirety of Minecraft), add in a block-dying system. OpenBlocks specifically adds in paintbrushes (the tool you use to apply paint to blockfaces), paint cans (placeable buckets containing the color info), a paint mixing machine, and stencils. I believe you can separately color individual block faces, rather than applying the paint to one face and having it color the entire block.