The water based poly is the reason they are lighter. Oil based poly ambers the wood slightly. Had they been finished with the same type poly they would have matched. Sanding probably wouldn't help now, since the new coating wouldn't be able to penetrate the treads.

What if I sanded it all the way to the bare wood?

Before doing all that sanding, try adding two coats of oil based poly.

In the future, more than three or four coats of either poly becomes redundant. There is no more protection added, and, since poly is prone to chipping and is very difficult to repair---more coats make deeper chips.

I use a name brand varnish for coating wood stairs. Just as much protection and better repair ability.

Can I just add the oil based over the water? I am guessing I should lightly sand first? Should I notice a difference in the color right away or do I need time to pass for it to yellow a bit?

I'll try to get a pic of it to post so you can see the color difference.

For the future what brand varnish do you use?

Thanks again!

OK, this isn't a pic of my floor but it looks exactly like my treads and the rest of my wood floor. I will get some oil based poly and try it on one and see if it helps -- if I could get it to amber even some. Any particular brand you prefer?

Here is a link that might be useful: Pic

I like Sherwin Williams Wood Classic varnish.

Any oil based finish adds the amber tint. I generally use Minwax, HD or Lowe's. You will see an immediate change.

Hand sand with 150 grit paper. There may be problems after applying the new poly---because of the number of coats on the stairs now---bubbling, checking, that sort of thing. I have used oil based over water based successfully in the past---but not over 10 coats.

If you have to remove the water based, stripping will be much faster than sanding---poly clogs sandpaper quickly.

Thanks! I am going to give this a shot tomorrow morning...will let you know how it works out!

Its definitly mellowed a bit...the blueish dead tone is gone. Its still much lighter, but at least its warm looking. Thank you so much for the tip of using oil over the water based poly. I used Minwax and it seems to have bonded fine.

Now if it will last.

The bluish 'dead' color is from water based poly. That variety adds no color.

Cross your fingers...so far so good.