This artwork was created by making a rounded step shape and then duplicating it once at a diagonal offset. I then reduced the opacity to 25% and grouped them. Then I duplicated them repeated at the same diagonal offset.
The overlapping of the partially transparent shapes created the other tones/colours and the apparent shapes.
I then cropped it to a square. This could be used to create a seamless larger pattern.
If you tilt your head to the right 45 degrees you can do that MagicEye thing…