Who said anything about achieving the colour of a wild bird?
Lad asked about improving the mask of his goldies. Carophyll red will frost the yellow wingbars of his birds which is a major fault if he wants to show them.
Only way to feed red to pates is to wait for the wingbar primaries to come through first then feeding it, the mask being the last feathers to colour up after the moult.
Yellow carophyll won't do this but will enhance the mask.
Far better in my opinion would be for the lad to get out and pick what the wild birds are eating I.e. Dock, plantain (rat tails), teazle,