Each LIFX bulb has a Wi-Fi chip, and a unique MAC address. The MAC address is printed right on the bulb base, and is also the serial number.
A MAC address is a 12 digit number. For a bulb with serial number D07123456789, the MAC address would be D0:71:23:45:67:89.
Currently, all LIFX lights have a MAC address beginning with D073D5. The last six digits of the MAC address are broadcast, as part of the LIFX Wi-Fi network during setup.
Now that you know the MAC address, you can assign a static IP on your network for each bulb. Or, if you have a MAC filter on, add the MAC address to your allowed connections.