caesi
Caesi is a Latin adjective meaning bluish-gray. In classical Latin, the term describes a hue between blue and gray, and in later color terminology the idea persists in descriptions of bluish-gray tones. The masculine plural nominative form in Latin is caesi.
In English, the root appears in several color terms derived from caesius, notably caesious and caesiaceous,
The root also provided the basis for the chemical element name cesium, or caesium. Discovered by Bunsen
Although caesi is not a common standalone noun in modern English, its derivatives survive in technical vocabulary