Adding material to one part changes all the parts - Help Please

Hello,

I have searched high and low and cannot obtain an answer on this.  I have an assembly and want to add a material to a part.  I can do that, but it will change all copies of that part with the material I pick.  This is a problem because they need to be separate colors.  Sure there are some tricks I can play to change it, but when I use my BOM it will still show all the parts with the same colors.   I searched options, thinking it was a default, but couldn't find anything.  Changing the material in the part, then bringing them in would work, but not the best option because we have a library of 800 parts.  This means if something changes, all the parts needed to be updated, vs one assembly file, which is significantly faster.  That is why I am adding the material in the assembly file.  Can anyone help me out please?  Thanks in advance!

SolidworksAssemblies