| Pigmentation | Melanin levels and distribution | Determines the range from blue to green to yellow. More melanin = darker eyes (green, amber), less melanin = lighter eyes (blue). |
| Albino Gene (C) | Affects tyrosinase enzyme | Cats with the albino gene (c/c) have very pale blue or pinkish eyes due to reduced or absent melanin. |
| Siamese Gene (Cs) | Temperature-sensitive version of albino gene | Causes blue eyes and point coloration due to partial albinism. Eyes appear blue as melanin production is restricted in cooler areas. |
| Dominant White (W) | Suppresses pigmentation in fur and eyes | Cats with the W gene may have blue eyes, often associated with deafness. If one eye is blue and the other is another color, it’s called heterochromia. |
| Oculocutaneous Albinism (OCA) | Rare form of albinism affecting eye color and vision | Results in pale blue eyes, often with vision problems. |
| Copper Eyes | Result of high levels of yellow pigmentation (pheomelanin) | Common in some breeds, such as the Burmese. |
| Green Eyes | Moderate levels of both eumelanin and pheomelanin | Common in many cat breeds. |
| Heterochromia | Condition where each eye is a different color | Can occur due to genetic mosaicism, injury, or as a result of certain genetic conditions. |