Yes, you can substitute Green Chartreuse for Yellow Chartreuse in cocktails, but expect a noticeable difference in flavor and potency. Green Chartreuse is more robust and herbal, with a higher ABV (55%), making it a bolder choice. Yellow Chartreuse, on the other hand, is milder and sweeter with a 43% ABV. When substituting, consider using a smaller amount of Green Chartreuse to balance the flavors, or be prepared for a stronger, more intense cocktail.