There is a red and blue light on the ceiling of the hotel, which keeps flashing. Does anyone know?

According to your description, this flashing light may be a smoke detector. Smoke detector is a kind of equipment used to detect indoor smoke. Its function is to find and remind people to take safety measures as soon as possible in case of fire. It is common to install smoke detectors on the ceiling of hotel rooms.

The light of this smoke detector may flash to remind people of its existence and work. Usually, the lights of smoke detectors will flash at a specific frequency, which is to attract people's attention and facilitate people's observation in the dark.

If you are worried about this flashing light or are not sure about its function, it is suggested that you consult the hotel staff or check whether the smoke detector in the room is installed normally to ensure that it is in good working condition.