Today I made a small sample board of the different colors associated with the metals I use in metalpoint drawing.  From left to right below are: copper, aluminum, .9999% pure silver, pewter, 12k gold, and .925 % Sterling silver.

I dated the card so that as the metals oxidize and age, color differences over a specific period of time can be known.  I mention that because some metals, such as gold, fade over time, and a gold drawing I did 3 years ago has all but faded completely. It is also good to know what hues are reflected, what colors are reflected by each metal, especially if combining the different metals in one drawing.  The support I used is marbledust and rabbitskin glue on heavy illustration board.