There are spares on the flashforge motherboard for connecting other parts that are not currently wired up - they appear to lack the circuitry behind them too.

MightyBoard.jpg

The white connector nearest the bottom of that picture - this is the RGB lighting connection. However have looked at a number of pictures and my own - it lacks the connector itself, the 3 parts directly to the right of it too (U16, U17, U18).
Mine is an earlier revision board than that one shown but is very similar (printer purchased less than a month ago)

The other option may the green connector (marked EXTRA) - but again this lacks the plastic connector and the parts downstream from it to drive it. (U19, Q6 - could be O6 can't make it out well) and the resistor array R10 through R15.
Unless your soldering skills are up to it (not doubting you can do it, just seems odd that you wouldn't have taken the lid off if you are that way inclined to investigate ) I wouldn't mess with SMD stuff personally. Even as a amateur electronics "tinkerer" for the sake of lights I would be happier to run a standalone setup driven from a 12V source - something like the Ikea Dioder setup would seem ideal or if feeling more adventurous - a full RGB set driven from a Adruino or the like. I am contemplating the later myself hopefully with some way to drive different colours based on build percentage and just bright white in idle while I setup etc.
Let us know how you get on though.