yellowness vs spectral color

yellowness and spectral color both are nouns.

Word	Noun	Adjective	Verb	Adverb
yellowness	Yes	No	No	No
spectral color	Yes	No	No	No

As nouns, spectral color is a hypernym of yellowness; that is, spectral color is a word with a broader meaning than yellowness:

yellowness: yellow color or pigment; the chromatic color resembling the hue of sunflowers or ripe lemons
spectral color: a color that has hue

Other hypernyms of yellowness include chromatic color, chromatic colour, spectral colour.

yellowness (noun)	spectral color (noun)
yellow color or pigment; the chromatic color resembling the hue of sunflowers or ripe lemons	a color that has hue