system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why when you press on your closed eyes is a sort of kaleidoscope pattern effect with blue, green, red, and white sparkles seen?
gpt
You are likely seeing phosphenes, a visual phenomenon caused by mechanical stimuli resulting from pressure or tension on the eye when the eyelids are closed. 

While temporarily rubbing the eyes is fine, note that pressing on your eyes will cause your blood pressure to decrease through a biofeedback mechanism and is not recommended from a medical standpoint.