Quoted from jadziedzic:

There are two sizes of insulation displacement connector commonly used in Bally/Williams games for board header connections: 0.156 inch and 0.100 inch. The two sizes are available in different varieties to accommodate different gauges of wire. The connector has a colored stripe to indicate the appropriate wire gauge: orange for 18 gauge, brown for 20 gauge, red for 22 gauge, black for 24 gauge, blue for 26 gauge, and green for 28 gauge.
The thicker wire on Bally/Williams games is typically 18 gauge while the thinner wire is typically 22 gauge.
The 0.100 connectors do not accept any wires larger than 22 gauge, so you can order just that single version (red stripe); the 0.156 connectors are either 22 gauge (red stripe) or 18 gauge (orange stripe) so you have to order the version appropriate for the wire used.