As stated very clearly above, copper and brass are highly reactive metals and will patina (change in color/appearance).
I have a Charcoal Goods copper razor in antique finish (forced patina). I (actually friend) applied a clear coat and I applied
Renaissance Wax (and will re-apply quarterly). In theory, should be very little color change and no change in the blade gap. I did the same on my Charcoal Goods brass razor.
Copper weights more than stainless and brass which could be an asset is some razor designs. I am guessing there are methods to clean copper (brass or chrome or ? polish). In US currency, the "1 cent penny" is made from copper - I have seen many brown pennies, however, never seen a green penny.