Applying textures to multiple meshes

I have a large grid of hexagons, i want to apply 4 separate textures to each grid. Then there is a script that allows the player to select one of the textures to apply to the tile, in effect laying a tile. But when i use a script to change any one texture. it changes the textures for the entire structure. how can i make it so the different tiles each receive it's own instance of a texture? i am trying out different options in the fbx importer's material tab, but no joy so far. Any clues?