Y level numbers can't be read on white-colored blocks

[Carmen14edo]

I'm working on a map art with many colors in it, but the background is white, and the majority of the pixels are white. I'm using staircasing but I can't read most of the numbers written on the blocks since a majority of the blocks are white and the font is also white. Hoping maybe someone could update it so the y level font color is dependent on what shade of block that pixel is. It'd be much appreciated.

[rebane2001]

Added in 177f405