If you mean a chart for colours when tempering silver steel after it has been hardened, Wong, here's one:
http://www.alexdenouden.nl/08/temper.htm . I'm a bit mystified by the difference between boring bars and boring tools, but it's very hard to tell the 5° C colour differences anywhere between 220° and 250°C.
I think the best practice is to hold the item at the required temperature for some time. My kitchen oven goes up to 280C, so suppose I could use that. I would need an oven thermometer; the oven thermostat and dial are not accurate, which is the excuse I use for my culinary failures.
However, in most cases I just play a flame below (rather than directly on) the item, away from the crucial parts like points and cutting edges, and watch the colours run along until those parts have reached something like the required shade, then remove the flame and allow to cool. Using a flame means that I can't hold the correct colour for more than a second or two, but it really doesn't seem to matter too much on small items.
Bedding the item in sand in an old tin which is heated from beneath gives more control, with slower colour changes. I do this on the gas hob in the kitchen. In fact, I do quite a bit of metalwork in the kitchen. Even when my wife was alive, she was very tolerant, being an engineer's daughter.
Andy
