I hope not. I have it and like it. I also just did my sunroom in the dark slate porcelain tile;)

It depends on how much light you have in your foyer. The dark slate could make the space feel small and dark, or it could work very well. You might post some photos of your foyer for more opinions. Another option is to bring home some samples of the slate and lay them out in the foyer to get a feeling for how it might feel....

It also does not show the dirt so I tend to overlook it when I am cleaning.

HI -- Why would it be a mistake ? If it will add some elegance then yes add some dark slate . If you are worried about it showing foot prints from dirty shoes then add a rug . Sounds like your ready for a change and I think it will look nice .

I have a very small foyer and it is dark. I want to put a light color down but not sure what to put or what type of tile. There is heavy traffic in this area