The purple and blue wires provide 115 volts AC (or VAC) to the input terminals of the transformer. You probably only need to use the Normal input tap. The Low input tap was more necessary in the 1950s when this game was made to allow for variability in supply voltage across the country. With 115 VAC pulsing through the primary winding (on the left side of the schematic) the transformer should generate 6 and 30 VAC at the outputs. In the game you should be able to measure 30VAC (or a little more) between the yellow and black wires shown in the schematic which is the supply for the solenoids, relay coils and motors. The 6 VAC for the lights would be between the yellow and whatever wire runs off to the light circuits (labeled J for jumper in the schematic). Note that the yellow wire is common to both the 30 VAC and 6 VAC circuits, but don't think of it as ground or neutral.

Before putting the transformer back in the game you might want to read up on how to make the game safer with a new line cord at:
https://pinside.com/pinball/forum/topic/replacing-line-cords-plugs-wall-sockets-vids-guide

/Mark