That's typically what happens when the parts come in contact with too much air during the quench,probably done by someone who was not very experienced in the process at the time, some people tend airate their quench water too violently and as a result expose the parts to too much air as the parts enter the water.
Nothing to do with temp or bone charcoal ratio, if you look at the picture carefuly, whatever colors are there they are vivid,..but the coverage is rather poor

CJ

The taste of poor quality lingers long after the cheap price is forgotten.........