Rejuvenate Exact Match Wood Furniture & Floor Repair Markers, 6 Count, Brown Markers Cover All Scratches, Scuffs And Damage To Wood Furniture And Flooring

Coloring markers. Either fancy wood repair ones like these: https://www.amazon.com/Rejuvenate-Furniture-Scratches-Disappear-Combination/dp/B00D8OKFP0 Or kids coloring brown and black (maybe red). You could first try some acetone and see if color from the rest blends into the lighter parts or at least makes the edges less pronounced.

https://www.amazon.com/Rejuvenate-Furniture-Scratches-Disappear-Combination/dp/B00D8OKFP0 That's exactly why I don't like it, because I am impatient, and it takes too many coats with acrylic markers.