almcl wrote:As Alacant points out above the question was actually about colour.
If there was any doubt, you can safely disregard the nonsense posted about colour.
There is a reason why star "colours" are not published in a convenient, autohritative CIE XYZ component table. That's because there is no one set way to derive XYZ tristumuls values from temperatures (let alone simple B-V values), without making a huge amount of assumptions.
I also see that Martin Meredith posted in that thread, proposing some star (intensity-less) colorings, based on a stackoverflow table/formula that converts GAIA survey photomteric values, a formula which itself is based on the vendian.org link I posted eariler in the thread.
The page at that link states;
All these numbers are approximate!
These are not magic values for pixel color. Each time I change the details of how things are handled, and then regenerate these web pages, different colors fall out. Quite similar, but different.
The choice of white point (D65 vs D50) makes a big difference. I.e., is the Sun bluish or pinkish. sRGB and Rec.709 both use D65.
The choice of gamma correction (sRGB vs Rec.709) makes some difference. And the chromaticities I derive from the various sources are not very tightly clustered. And I may well be making mistakes.
For each type/class, I am blindly averaging (in XYZ space) together the chromaticities of the spectra I have available ( Kurucz, Silva, Pickles ), or of the blackbody chromaticities ( Handbook, Tokunaga ) if I have none. This approach unfortunately creates color discontinuities as one jumps among data sets. I am also missing data on assorted class/types.
What are possible improvements? There are few enough class/types that one could hand craft a set of colors. I am unlikely to do this. One might interpolate missing class/type colors to get a more complete set. Look more carefully at the spectra to determine the sources of variance. Get more complete spectra sets (Kurucz comes to mind). Provide ranges of color
The colours in the table are only true for one gamma (close to 2.2), for one (arbitrary) white point (6500K) and for normalised intensities. Not for custom stretches, not for point lights of various intensities diffracted by atmosphere and optics, not for different white points.
But they, don't take it from me, because I apparently "don't understand" standard illuminants to begin with!
