> Because they're a real physical object whose colour properties cannot be accurately reproduced in an image using standard RGB colour. 'Real physical objects

> Because they're a real physical object whose colour properties cannot be accurately reproduced in an image using standard RGB colour. 'Real physical objects' don't have 'colour properties', as grouping together certain wavelength ranges of EM radiation and then assigning them a 'colour' label is a human invention. For example, even if every human disappeared from Earth tomorrow, objects will still emit EM radiation, but won't emit human invented labels.