What light are you judging the color of your steel? Old forge shops were kept dark for a reason. Some smiths even kept an empty barrel to stick their steel in to get a better take on the color of the steel if the shop was to bright. You talked of using the green Iridum glasses but I have never cared for them when tempering steel a good pair of safety glasses with UV coating works best for me. My advice is keep your shop dark . I used old kerosene lamps set at a distance when I was hardening & tempering steel without an oven. I also just liked the vibe of that type of light.