By viewing the red light on the bottom of the Apple Wireless Mouse, you can determine whether the mouse is turned on and correctly paired with your computer.
The light can be in four modes. Find your mouse's light in the list below to determine what state your mouse is in.
Solid red light - Paired
A solid red light means the mouse is turned on and paired with a computer. The red light will also stay solid if the mouse is being moved.
Slowly flashing red light (blink, blink, pause) - Can't Find Computer
If the light is slowly flashing on and off, this means the mouse is looking for a computer to pair with. For more information, see technical document 86468, "Bluetooth: How to Set Up Your Apple Wireless Mouse".
Quick flashing red light - Saving Power
If you do not move the mouse for one second, it will go into a low power mode (indicated by a quick-flashing red light). The quick flashes may slow down over the next few seconds - these different flash speeds indicate various levels of low power mode.
No light - No Power to Mouse or Mouse is Asleep
If you've turned on the mouse and the light doesn't turn on, try moving the mouse on an opaque surface. Make sure the host computer is not asleep either. If the light still doesn't turn on, the battery levels may be too low to power the mouse. Replace the mouse's batteries. See technical document 86472, "Apple Wireless Mouse: How to Install or Replace Batteries".
If the light doesn't turn on after you change the batteries, the mouse may need to be repaired. Call Apple for instructions on this.