Custom Building Products StainBlocker 32 oz. Stain Resisting Admixture Additive for Grout SBG32 - The Home Depot
3 Easy Steps to Change Grout Color From Dark To Light or White (FAQs And Video Too) - Abbotts At Home
Recommendation to darken grout. This Prism Natural Gray came out a shade or two lighter than the swatch and is not the look I wanted. I want/need a more muted grout line.