Starting with the leaves is an smart move to set the place for owl. In my view, a snowy owl look will b stunning, mostly white with few charcoal or light gray spots for texture. More options would to go for great horned owl with deep browns, warm tannings. iconic yellow eyes will pop against darker markers. Its always fun seeing how the 1st owl develops alongside the greenery. happy coloring, cant wait to see the progress....
For owl color reference you can checkout this page on GettyImages