YThe gen 2 says colour 1000 on the bulb itself under the LIFX logo (also it’s a darker stone white colour bulb casing) the gen 3 only has a logo and does NOT say colour 1000 under the logo (its casing is a pure white colour ).
The gen 2 also has a venting ring between the screw fitting and the bulb. The gen 3 is sealed all the way up.
The confirming factor for it being a gen 3 bulb is that they say 1100LM just above the screw fitting. The gen 3 bulbs output 1100 lumens where as the gen 2 output 1055 lumens