Resizing Pictures is harder than you think!

level3

Downscale use various algorithms (calculation methods).
The downscale image will look relatively normal if it use "near neighbor" method
It will turns gray with Lanczos or Gaussian. And their gray patterns are different too.
The image is probably designed to show algorithm problems, its not a monitor problem.

Downscale methods may vary on different platforms: browsers or software.
If your image software is good enough, it should allow you to choose which downscale algorithm to be used.