Say you stain an object with a store-bought oil (“wiping”) stain and the color is too dark. Assuming you haven’t yet applied a finish, how do you lighten it?
Most importantly, don’t sand. Whatever you do, you have to do the same everywhere to keep the color even, and you won’t be able to control the depth you sand to evenly.
It’s much better to try wiping with naphtha. It’s a little stronger than mineral spirits. See if it pulls out some of the color. What you’re trying to do is break down enough of the binder that holds the pigment particles together and to the wood to lift some of the color.
If this doesn’t work, try acetone or lacquer thinner. If this doesn’t work, try paint stripper—any kind. This will be messier, which is why I’m suggesting it last. You ought to be able to remove enough of the color with one of these solvents.
But if you’re still unsuccessful, you could try rubbing with steel wool. It will be easier to rub evenly with steel wood than with sandpaper. You could also try using the steel wool together with one of the solvents to see if that helps. The most important thing is to try to keep the remaining color even.