Umm, agreed...what? Please do clarify what you're asking, so we can better help you. What white matte are you speaking of? What types of cards, exactly? Where on the card? You know...the important details about what you're actually asking. As it is, I have no idea what you're asking.
As it is, it looks like you're asking if you add a white matte finish to a card, will it show up? To which I would respond, is this white matte finish opaque, or is it translucent (or semi-translucent, or whatever)? If it's like a white-out type material, then yes, it should show up on the coloured portions, and would probably blend in pretty well with the white areas (although it would reflect light differently than any other white portions of the card, so it may go unnoticed, but the potential is there for others to notice it). If it's another type of material, then like I said, please do elaborate for us so we can help you.