1 of a dull greyish-green or blue colour; pale grayish or bluish green.
2 having a powdery or waxy coating that gives a frosted appearance and tends to rub off
As at Walden, in sultry dog-day weather, looking down through the woods on some of its bays which are not so deep but that the reflection from the bottom tinges them, its waters are of a misty bluish-green or glaucous color. (Henry David Thoreau, Walden & on the Duty of Civil Disobedience)
Friedrich's own Landscape with a View of Mt Milleschauer, possibly unfinished, is a desolate near-abstract without figures or even more than notional vegetation, in five dismal glaucous shades. (Brian Cubin, Pictures from Dresden at the Royal Academy., Contemporary Review, June2003)
Mrs. Bodiham looked at him; her pale, glaucous eyes reflected his action without comment. (Aldous Huxley, Crome Yellow )
'dull bluish-green, gray,' 1670s, from Latin glaucus 'bright, sparkling, gleaming,' also 'bluish-green,' from Greek glaukos, a word used in Homer of the sea as 'gleaming, silvery' (apparently without a color connotation); used by later writers with a sense of 'greenish' (of olive leaves) and 'blue, gray' (of eyes). Beekes says it is probably a substratum word from Pre-Greek.
Homer's glauk-opis Athene probably originally was a 'bright-eyed,' not a 'gray-eyed' goddess. Greek for 'owl' was glaux, perhaps from its bright, staring eyes, but this, too, might be an unrelated Pre-Greek word. Middle English had glauk 'bluish-green, gray' (early 15c). (Online Etymology Dictionary)
Glaucous came to English - by way of Latin glaucus - from Greek glaukos, meaning 'gleaming' or 'gray,' and has been used to describe a range of pale colors from a yellow-green to a bluish-gray. The word is often found in horticultural writing describing the pale color of the leaves of various plants as well as the powdery bloom that can be found on some fruits and leaves. The stem glauc- appears in some other English words, the most familiar of which is glaucoma, referring to a disease of the eye that can result in gradual loss of vision. Glauc- also appears in the not-so-familiar glaucope, a word used to describe someone with fair hair and blue eyes (and a companion to cyanope, the term for someone with fair hair and brown eyes). (Merriam-Webster)