In my world, paying attention to a dragon's scales is a matter of life and death. If you noticed a dragon with a brassy sheen to his scales, you are most likely to be forced to be part of his conversations for a very long time, or you might find yourself robbed by a copper. However, a dragon with red scales will more than likely torture you for just the entertainment value. Chromatic dragons, the ones with black, green, white, blue, or red scales are those to be avoid at all cost. They don't have the merciful tendencies as metallic dragons do.