yeah color temperature, Kelvin, like 3,000K, 7,000K, 10,0000K?
This one?
https://www.rollitup.org/indoor-growing/104309-400hps-versus-400mh.html
Did you start with clones of the same pheno? You can't really say "the one under MH produced bigger denser buds than the one under the HPS light." if...