[mega_dean]

I stared at this one for a long time: https://hidden-3d.com/index.php?id=gallery&pk=457 They use opposite colors for the foreground which makes it look opalescent and gray at the same time.

[Julien_r2]

Ah the fading colours experiment! Interesting one! I'm still not grasping the efforts it takes to create those effects..

[cubefox]

I find this effect somewhat unpleasant to look at though.