Gray wood could be recoloured.
As for stair, slab etc. blocks, maybe they are not quite as essential for the rainbow colours but they would be handy for grey and white wood. Implementation would be the same as with regular wood blocks, with white wood representing weirwood (such as the Bower).
As for stair, slab etc. blocks, maybe they are not quite as essential for the rainbow colours but they would be handy for grey and white wood. Implementation would be the same as with regular wood blocks, with white wood representing weirwood (such as the Bower).