This old saying actually has a scientific explanation. It relates to moving high and low surface-pressure weather systems, and the way that the colors in sunlight are scattered differently by dirty and clean atmospheres. This is the explanation of how these phenomena combine to color our sunrises and sunsets.
If you look at a global map of surface pressure, you will see a string of alternating high-pressure and low-pressure areas. That is because pressure patterns are relative; i.e., if a region of lower pressure exists, it must have higher pressure on either side.
Low pressure is associated with bad weather (sailor take warning), and high pressure with good weather (sailor’s delight). Low pressure causes air to converge (to try to “fill” the low), and converging air causes upward motion, which in turn produces clouds and precipitation.
In contrast, air diverges from the center of a high-pressure area. This causes downward motion, which suppresses cloud formation.
Read more at this link.
(Image via @TheTraceyKay on Twitter)