I’m working on a travertine shower. The issue is that the tiles below the marble border are darker the tiles above the border. I cut it with 120 sand papers and it did lighten the stone, but it still does not match the upper section. I’m hesitant to keep cutting due to concern that I will open up a lot of holes. My other thoughts are to poultice the lower section with hydrogen peroxide, but that could possible involve number of trips to the job.

Any suggestions appreciated!

Please see attached pictures. I took the picture will the stone is wet so they are darker than when dry.