Question about reading spark plugs

I think I once saw a comment by Rick that indicated the best way to read plugs was by looking at the ground strap coloration. Anyone know where I can find that information.

I just adjusted and synced my carbs and used a colortune plug. I closed the pilot screws until the engine started to slow or stumble and the blue began to fade. Then I opened the screws until the blue returned and the engine idled smoothly. I installed new plugs and went for a 20 mile ride at about 60 mph. The plugs are very clean and have a slight brown color on a portion of the ceramic, but not all the way around. the bike runs very well, cranking, idling, accelerating, etc.

I started my adjustment from a lean position in order to see the color of the plugs change if adjustments are required. I think I may be a little lean, but these plugs look exactly like the ones in my Honda Rebel where the carbs have never been touched.

So if someone knows where to find the information on reading the ground strap please let me know.