Siamese cats get darker in winter because of temperature changes. A mutation in the TYR gene within their bodies alters the synthesis of tyrosine, causing their fur to darken in cold weather. However, this usually only affects darker areas like the face and tail; other parts of the body generally remain unaffected.
In addition, there are other patterns in the color changes of Siamese cats' fur. Siamese kittens are generally lighter in color, many even resembling white, but as they grow older, their fur color will become darker. These are all normal phenomena. 
Yes, it can turn back to its original color. Siamese cats are cats whose fur color changes with temperature. If the temperature is too low and the Siamese cat feels cold, its fur will turn black. If the temperature is warmer or returns to normal, its fur will turn white again. The color of a Siamese cat's fur changes with temperature; whenever the temperature changes, the fur color will change accordingly. To prevent a Siamese cat from getting darker in winter, take measures to keep it warm, such as feeding it warm water and warm dog food, maintaining a temperature of around 27-29 degrees Celsius, and avoiding feeding it raw or cold food. You can also increase the indoor temperature by turning on the heater to prevent it from darkening.
