how can i fix rear fog light problem?

no rear fog lights, relay clicks, light on dash comes on, so assume switch works. have connected live feed to rear light (blue/black) both fogs come on. checked drivers side loom found 2 blue/black wires pierced them with pin no output when switch on. when switch off if live is connected there is a flash, probably a short & no lights. haynes says red/black feeds rear fogs doesn't seem to be the case no supply voltage when checked with switch on. at my wits end will get a switch & supply it direct if no fix suggested