Thanks Nick,
I was familiar with colour measurement (CIE colour space,tristimulus values etc using standard light sources C, D65 etc) from my life in the paper industry but it was the definition and determination of the correlated colour temperature of the light source which I was particularly interested in. Following your lead I found this specificwikipedia page
https://en.wikipedia.org/wiki/Color_temperature
I wondered about the usefulness of the definition of CCT for light sources like LEDs which have spectra which deviate significantly from a smooth Planck curve. (Rather like trying to measure Teff of a star from the continuum shape in the visible region, a source of much confusion to beginners when they fail to get the “right answer”) The wiki page does caution about the range in which it can be used but the second plot I posted does at least suggest a good correlation between CCT and “blue light hazard efficacy” for a range of light sources regardless of their spectrum shape
Cheers
Robin