You’ve got options. 

The most environmentally friendly option is to use the paint for another project (any project!). And, know that once opened and used, the paints have a short shelf life. We suggest using the paints within 1 year of opening.

The next best option—and in order to keep micro plastics out of our oceans—is to let the remaining bits of paint dry out, then drop everything into the garbage. It may sound surprising, yet this is more environmentally friendly than rinsing the remaining paint down the drain and recycling the glass.