Scarlet Red Meaning

Example: Used other than as an idiom: see scarlet,‎ red.
An azo dye used to treat wounds and ulcers and as a histological stain.
2005, Avi Shai, ‎Howard I. Maibach, Wound Healing and Ulcers of the Skin, page 219:
  Scarlet red is an aniline dye which has been used in the treatment of wounds and ulcers since the beginning of the past century.
(Can we date this quote?) Ivan Nikolaevič Filipév, ‎Jacobus Hermanus Schuurmans Stekhoven - 1959, A Manual of Agricultural Helminthology, page 195:
  The staining may also be done in a saturated solution of scarlet red in equal parts of 70% alcohol and acetone....