In my experience all the aluminum panels are horrible. They are weak, damage easily, and the detail is really bad. While aluminum won't rust it is almost a guarntee that you will damage it badly durring installment. The last post is correct that you will need to at least seal the steel panels before you installthem but any clear spraypaint will work. While you sy that you don't want to paint your ceiling I would still suggest checking out www.valleytinworks.com the site shows all kinds of more contemporary paint schemes that you might really like. You can also see what the various patterns will look like. I hope this was helpful

You know the answer already. Remove the tiles and deal with the cutback.

ok,,that's what I thought. then I think you may have a problem. not many people know that these tiles MUST be sealed before install. they are very porous. when the grout goes on, it should not be spread out over the tiles like regular tiles, especially if not sealed. the tile absorbs the grout material and it can stain. Now I don't know if this was done to yours, but you could try some grout release and see if it cleans up. you need to ask,,, were the tops (seal tops only, not the sides) of these tiles sealed before installed? a way to find out is water should bead up on the tiles. if the water absorbs, not sealed. when the tile setter installed them on the wall, did he dunk them in water first? if not, a dry cement tile will quickly suck up all the water from the mortar and possibly lead to poor adhesion. what kind of grout was used? here, read this page for more info. look at the grouting and sealing heading. read carefully: https://www.cementtileshop.com/INSTALL.html If that tile is discolored and won't clean up, hurry up and take it off before it hardens and cures. replace w/a new tile. wash all those tiles well, let dry and seal multiple times (every 24 hrs or so) until no more sealer is absorbed.

The contractor's response makes no sense and you are wise to have an experienced, dedicated tile professional on site to evaluate it. As for use of glass tile mosaics on shower floor, yes, some are recommended for that use. Refer to the manufacturer recommended uses (it sounds like you did that for yours). The installer you used likely was not experienced with glass tile installation methods and/or basic shower installation. Make sure you vet the experience of the new installer. Good luck.