Ok everyone... Let's try to stay on track with the original discussion... dye for sand to be used in a saltwater tank. If there's anything more to be shared, that's perfectly fine, but let's remember there are freshwater products that are not suitable for saltwater use and vice versa.
Considering the sensitivity of marine microfauna to any number of contaminants, I would agree that it would not be wise to use any sort of dye on sand or anything else intended for a saltwater tank.