This may be a basic question.... but what is the best ambient lighting for interpreting heating colors of the steel you are working on?  Dark, sort of dark, typical shop lighting??

Not dark dark, but really subdued. I use a trash can on it's side during daylight. Pull it out of the fire & stick it in the can then look for the color.
The really best way is a pyrometer to tell you the precise temp.
Everyone sees colors differently so you're going to have to experiment a little.

Larry

How about those infrared remote thermometers mechanics use??? I saw somebody using one of those at Haywood.  He just aimed it right at the edge of the blade...