Revisions log for Answer #1038

The waviness can indicate either a defect or clearly corrugated glass.

In my opinion, most window glass today is produced using a flotation process, resulting in a very flat surface.

The purple color is due to the coating of the glass, whose job is to let more blue color inside the house, which means there is more daylight in the house, but the insulation remains intact. (Usually with triple glazing).

It's also possible that the window panes have an anti-glare coating. In this case, the light shimmers from purple to green. It depends on what the builder ordered or what the home building company has in the standard.

Windows that don't shimmer purple have no coating or often have only double glazing.