Paul,

Using acrylic artist colors will work well if you also use an additive. I use a clear medium gel that turns any opaque color into a translucent varnish. This way you can also see the grain of the wood where you patch it. I use Liquidtex brand "Gloss Medium & Varnish" That and an appropriate dark brown shade should make it easy to to the repair. After sanding do a saturation coat of epoxy to seal all surfaces. Then use the acrylic color with gloss medium to darken the light areas without opaqueing out the grain.

Steve Pituch