Why does the blue label appear green?
FAQ from Trevigen
The green appearance is due to oxidation (presence of bleach, metals, and other oxidizing agents.) Make sure to wash in deionized water before and after the TACS Blue Label™ step. Ensure work bench, pipettes, tips, etc are not contaminated with bleach or other strong oxidizing agents.
Methyl Green may have been mistaken for TACS Blue Label™. The methyl green can look blue prior to the ethanol washes and fades to green as excess dye washes away.