Dyes used for Bath Salts

[Synascents]

To get a really nice vibrant shade of color for bath salts, other then B&B safe liquid dyes, what other dyes can I use to achieve this?

TIA

Stephanie

[Jadryga]

I think water soluble food coloring works as well, but I can't remember, it's been a long while since I've done bath salts.