upload it to a file host and link to it.  i think your problem though is that your changing the color of the same material

to test this change the name of one of the materials and see if the rest change as well

blender works by not making each material for each object but by making universal materials and allowing you to apply them to the objects.  

to fix this next to the name of the material there is a scroller. click on the scroler and click add new material.  name your new material and change away.  i doubt its a bug because i never have any trouble like this with materials