Well, I think this is a problem that has many angles to it. "Greattoning" on ebay sells enormous quantities of toned goodies, The colours on the Battle Creek Morgans is something to see with neon pinks, greens, yellows, etc.- take a look at these if you have the chance. I have read some scientific papers embarrasingly beyond my comprehension mainly related to the microchemistry and interfaces of semi-conductor chips, and also charged ion electrodeposition - I wonder if they may be employed in generating some of these wonders??