I recently had my stairs refinished professionally with an oil based finish. Now that they have been refinished it is apparent that the 3 top stairs are much darker than the bottom 11 stairs. I suspect the material is different but was later stained to match.

Now that I have an oil based finish, my plan is to stain a water based urethane and topcoat the bottom 11 stairs so they are closer in color tone.

Any issues with my plan? Thanks.

Water-based poly-urethanes are clear, but can be colored with either liquid or powdered dyes. Sometimes it will be necessary to add two coats to make a significant color change. Water-based poly will wear differently than oil-based. You may want to coat all the steps with the clear water-based after you get the right color so the gloss level and wear characteristics are the same.