2,555. Permitted Colors

Hilchos Shechita 7:18

If a lung is found to be the color of date-palm branches, we prohibit it out of doubt because it’s very close to a prohibited color. We don’t prohibit any of these colors until the lung is inflated and rubbed. If doing so changes the lung to a permitted color, the animal is permitted; if the lung remains the prohibited color, the animal is prohibited.

Hilchos Shechita 7:19

There are four permitted shades: black/blue, green like a leek, red and the color of liver. Even if a lung is completely a patchwork of these four colors, the animal is permitted.