2,554. Prohibited Colors
Hilchos Shechita 7:16
Let’s say that a lung changes color, either in part or in whole. If it changes to a permitted color, it remains permitted even if the whole thing changes color. However, if even the smallest part of it changes to a forbidden color, the animal is a treifa because a prohibited color is comparable to a puncture, as has been explained.
Hilchos Shechita 7:17
Five shades prohibit a lung: black like ink, green/yellow like hops, like an egg yolk, like safflower and like the color of meat. Safflower is a plant used to dye clothes; it’s like hair that’s a little red, approaching green (i.e., orange).