https://www.alamy.com/stock-photo-the-u ... 54364.htmlHere's a good example (albeit, a restoration) of US Navy Buff in full daylight. But note that the upper buff section appears to be slighter lighter than the lower section. The word buff comes from the French "boeuf" which means beef, or most any bovine. Coats made of tanned cow, bull, and elk hides were the fashion in 17th Cen European armies.
https://en.wikipedia.org/wiki/Buff_coat ... 98.3_F.jpg In English, "boeuf" became "buff", hence the name "buff coats", and the name of the color.