When the weather is fine, close your eyes for a long time outdoors and suddenly open them, you will feel blue in front of you.

It's normal, because you close your eyes for a long time, and the light that enters your eyes through your eyelids is red. The eyelids are thin, there are many capillaries, and the blood is red, so the only light that passes through is red. When people stare at a wide range of colors for a long time, their eyes and brains will make adjustments to improve the color resolution efficiency. Therefore, the eyes and brain will be particularly sensitive to the light that can stand out relatively. If you close your eyes for a long time and watch red light, blue light will appear. Similarly, watching green light for too long will also show red light.