Another option would be to use colour correction gels like from Rosco. They publish transmission curves for their gels: https://emea.rosco.com/en/products/filte

Another option would be to use colour correction gels like from Rosco. They publish transmission curves for their gels: https://emea.rosco.com/en/products/filters/r3220-double-blue-ctb https://emea.rosco.com/en/products/filters/r3220-double-blue... (click on the little i). You could take pictures of the light source through a set of different gels and reverse to an approximation of the spectrum of the light source. Interestingly they are also now offering gels to correct the colour casts of LED lighting: https://emea.rosco.com/en/product/opti-flecs https://emea.rosco.com/en/product/opti-flecs There are samples swatches of their gels, which can be had by either asking a theatrical lighting supply company or on eBay.