It’s someone fundamentally misunderstanding an actual fact (that blue colors in nature almost never work the same way as normal pigments, and are a physical structure refracting light instead of a chemical that absorbs other light frequencies and reflects blue ones) as meaning something isn’t “really” blue. Like the feathers aren’t a blue pigment that could be dissolved in some base and used as paint (presumably) because their color is a structural rather than a chemical property, but it’s just silly to decide that the ontology of something “being a color” is dependent on chemical pigments instead of what it literally looks like when exposed to light.
It’s someone fundamentally misunderstanding an actual fact (that blue colors in nature almost never work the same way as normal pigments, and are a physical structure refracting light instead of a chemical that absorbs other light frequencies and reflects blue ones) as meaning something isn’t “really” blue. Like the feathers aren’t a blue pigment that could be dissolved in some base and used as paint (presumably) because their color is a structural rather than a chemical property, but it’s just silly to decide that the ontology of something “being a color” is dependent on chemical pigments instead of what it literally looks like when exposed to light.