electromagnetic-radiationtemperaturethermal-radiationwavelength
According to this picture
the light emitted by an object depends on its temperature.
That makes perfect sense when we heat a metal. As its temperature raises we see it red at first, then orange, then yellow… and then?
If we heated it even more should we see the metal turning green? and then blue?
Just to add to Vineet's answer. Wien's displacement law only tells you the peak wavelength of a hot object's spectrum. The actual emmission spectra is a broad function and so a hot object will emit both longer and shorter wavelengths.
Remember also that a hot object will emit overall more power, and finally you have to include your eye's sensitivity to various wavelengths.
So a piece of hot metal will appear white because although it's peak emmission will be in the infrared it is still emitting a lot of power at shorter wavlengths and your eye is more sensitive to blue than red.
There are 2 different kind of flames, and thus of flame color mechanisms:
Best Answer
You would be unlikely to see green. The problem is that in order to see green, you would need the spectrum of emitted light to peak at green and have relatively little contribution from other frequencies. This, for example, is the reason you do not see green stars (There is a cute Feynman story about this). An explanation of color temperature is given on wikipedia. Here is the path a black body takes with temperature increase--a Planckian locus diagram .