Turkish gravy train. Best Travertine is finished in Italy. We refer to Trav as Cunchy bar. Had a shop once chips blemishes filler etc all part of natural stone !! I usually go and select my pallets of stone from North London.
that looks about right for travertine it just needs grouting and as long as there is no lipping it should look ok.It would have been better if the tiler graded the stone before fixing and had used wedges instead of spacers.The grey comes from the silicate that is natural to stone.Make sure you do not use too much stain stop as you will darken the colour,max 3 coats