There is a wood filler product that is basically saw dust and some kind of glue paste. I don’t know the name but the old guy that was helping me with the house had about a half-gallon left over from a floor job. It was very light color and we couldn’t use it when we sanded my chestnut floors and he left it behind. When I went to do the cat clawed banister, I needed something to fill these deep gouges and that was all made from red oak and all I had was this light paste. I added a dark oak stain to the floor filler paste a little at a time and got it to match perfect.
You might try in the future mixing the stuff you bought down with a lighter product and see what happens. I did it by adding stain but I would think mixing two pastes together would be the same idea.