Blue
From Proto Indo European bhlewas, meaning “light colored”, applicable to anything from yellow to light gray to pale blue. In Proto Germanic this became blæwaz, and descended into Frankish as blao and Old French as bleu; this was borrowed as bleu or blwe in Middle English (when spelling was a creative art). Old English already had a perfectly good word for blue — blaw – but the French term was preferred. It’s uncertain exactly when the word changed from meaning “light colored” to “blue”, but color words tend to be slippery in that way — in Scandinavian languages, for example, it came to mean a deep black, while in Middle High German it meant “yellow”.
Energetically, blue is much like a fountain of water — a burst of liquid energy, flowing, fast-moving. Compare it to its homophone blew, and remember the music named after it, the Blues – these words have the same energy.
