Re: why colurs do exist due to heat (or energy) ?

Thank you for your question. Color is perceived - thanks to remarkable 
construction of the human eye and optic nerve. So first, I want to 
mention some basics of color and its relationship to heat. We perceive 
the color white if all wavelengths of light are equally reflected - our 
eye "integrates" the color spectrum. If something absorbs at a particular 
wavelength, leaving (say) red and green - the human eye perceives it as 
yellow, even though the wavelengths spectrally are a combination of red 
and green. So what we call color, is simply electromagnetic radiation of 
a particular wavelength. What we perceive as color (with our eyes) may be 
electromagnetic radiation of that wavelength or it may be a combination 
of other wavelengths which the eye integrates to perceive a particular 
color.

Next, the relationship between heat and light. Heat is just another form 
of electromagnetic energy. For an perfect radiator, the spectrum of 
wavelengths emitted due to temperature is given by the Planck equation 
(see, for reference:  http://physics.scsu.edu/~dms/cosmology/bBodyLessons/bb.html ). It is 
important to note that these "colors" are not limited to the relatively 
narrow band in which the human eye operates. Nevertheless, the thermal 
stimulation of the atoms and electrons emit electromagnetic radiation 
characteristic of its temperature. The sun for example has a surface 
temperature of a little less than 6000 degrees Kelvin. It peaks at around 
550 nanometers (yellow), which remarkably is the peak response of the 
human eye!

Anyway, I hope this helps explain color/heat a little better. I've added 
a couple of links here which go into a little more detail.
 934381368.Ph.r.html
 http://www.micro.magnet.fsu.edu/primer/java/colortemperature/index.html