Gel stain

There are a few things you can try to lighten the gel stain on your steel door:

1. Sand the surface lightly with fine-grit sandpaper to remove some of the excess stain.
2. Apply a coat of paint thinner or mineral spirits to the surface with a clean rag. This can help to lighten the stain and even out the color.
3. Apply a coat of a lighter color gel stain over the existing stain.
4. Allow the door to dry completely and then lightly sand the surface again.
5. Apply a coat of clear polyurethane to seal the new color and protect the door.

It's always better to test the color on a small inconspicuous area before applying on the whole surface.