>> That said I'm unclear how safe direct exposure to the pigment itself is (such as when suspended in a liquid for painting). There's not a lot of data available that I could find, and of course due to having a unique crystalline structure it won't necessarily have the same properties as the component products, however cobalt(II) oxide itself is extremely hazardous which is at least cause to be cautious.

The consensus is that artists' colours are hazardous waste that needs safe disposal. You can find instructions how to do that in many arts supplies' sellers sites and the like, for example one I've used:

https://www.jacksonsart.com/blog/wp-content/uploads/2025/04/...

The comment about not licking your brushes is a reference to the common practice of licking them in the wargaming miniatures painting community (you know, Warhammer and all that). You can find videos of influencers explicitly telling you that the best way to shape the tip of your brush or remove excess water is to lick it. For example:

https://youtu.be/BXMhwPAee4U?si=WM-FXuxDtToNpkm4&t=129

If you ask for a rationale it's usually that wargaming and generally hobbyist paints are non-toxic, but the truth is that hobby paint manufacturers never list their paints' ingredients so there is no way to know. And of course there's different degrees of toxicity, not everything needs to be cobalt(II) oxide-level toxic to hurt you if you consume "large enough" quantities of it; the question is what that "large enough" means and without knowing the substance, there's no way to know.

So: don't lick your brushes.