Another good colorant for epoxies that will be used to set stones
is stone dust. If you’ve got some of the stone rough, sand a small
pile of stone dust in a baggie or other small container. In a
pinch, the dust can be sanded from the bottom of the stone to be
set, assuming it’s thick enough. After the ‘stone dust’ has been
accumulated, mix the epoxy & hardener. When they are mixed, add the
stone dust to the epoxy & mix in thourghly. The color should match
very, very close.
HTH
Dave