Not fond of that term, it's Nicks. Epoxy doesn't take stain so you'd have to try to match the ending color with the filler, not an easy thing to do. Even clear finished wood gets colored by the epoxy varnish, so even if it's not stained the epoxy/wood filler will stand out color wise against the rest of the wood.

I use water based wood filler and you can buy it in different colors, even then you have to use care to try to match the color. Wetting the wood will give you an approximation of the colors you'll get.

Bill H.