Acrylic paint (the binder for acrylic paint is basically like glue.. it will stick to almost anything that isn't excessively oily)
Since these are on your fretboard, you will want to either use a heat curable acrylic paint or put a light coat of poly on top
I painted some inlays on my fretboard green and none has come off after 6 months of playing. I used createx airbrush paints which are heat curable, I used a heat gun (very carefully) but you can cure them using a hairdryer as well. Also BTW I applied the paint with a q-tip, not an airbrush =)
Another nice thing about createx line is they make most of their colors in both opaque and transparent versions, one of the transparent yellow shades should do a good job of tinting the inlay without completely obscuring the underlying pearloid.