This is the smoothing cap for the 18 volt line which is for the CPU controlled lamps.

Check for AC voltage on the purple wire, it should be less then .5 volts AC.

I don't normally replace those large can-sized capacitors unless there's an actual problem (and so far, I haven't encountered any issues). They last a long longer than the small caps normally found on circuit boards, and are a different grade.

Don't change it. It's not something you need to fix today. If something goes wrong with the game, we will help you troubleshoot what's wrong and fix it. While likely will not be that cap.

In all the years and games I've gone though I've only replaced one that was failing. It was on a 1979 Tri Zone and over 35 years old. When it was failing the lamp matrix slowly strobed from dim to bright, but it still worked. Don't bother replacing it. If it goes bad it will mostly likely be gradual, no harm will be done, and you'll know it.