"Some Clouds Have a Golden Lining."
Here is yet another amendment to the popular saying! The lowering sun's rays assume more yellow hues as they pass through a larger section of the earth's atmosphere. This filters out light from the blue end of the visible spectrum, leaving predominant yellows, then reds, as the sun sets. The high-based cumulonimbus (thunderhead) here was weakly rotating and LP (low precipitation) in character, rooted above a relatively dry and deeply mixed boundary layer with surface temperatures above 100 degrees F. Within about an hour, the thunderhead (which had almost no rain) would move northeast and help to compose one of the most spectacular sunsets of the season. This was a "backyard chase" of about 15 miles with my family, after leaving the annual NSSL summer picnic.
Oklahoma City OK (20 Jun 98), looking W.