ὑακίνθινος, -η, -ον (< ὑάκινθος), [in LXX for תַּחַשׁ, תְּכֵלֶת ;] of hyacinth, hyacinthine (see: ὑάκινθος), "doubtless meant to describe the blue smoke of a sulphurous flame" (Swete): Rev.9:17 (Hom., Eur., al.).† (AS)
Thayer:
1) hyacinth, of the colour of hyacinth 1a) of a red colour bordering on black
ὑακίνθινος
huakinthinos
hoo-ak-in'-thee-nos
From G5192; “hyacinthine” or “jacinthine”, that is, deep blue