The tiler has applied paving sealant to new brushed travertine floor tiles and im horrified some have gone too deep a color and they are now shiny how can you remove the sealant now its dried?

Could you specify exactly what brand sealer it is and exactly what type of sealer? Also the best suggestion might be to contact the manufacturer since they can have different specifications. Also if you do manage to get it off use a penetrating sealer or a stone specific travertine sealer.