This table provides the standard Lucas wire colour codes used in Triumph TR3s. I have added the Lucas codes for accessories that might be added to a TR3, such as driving lamps, radio and electric fan.
This table is the work of TeriAnn Wakemen
Black - All ground connections
Black/Green - Relay to radiator fan motor
Blue - Headlamp connections
Blue - Headlamp switch to dimmer switch
Blue/White - Headlight high beams
Blue/White - High beam dimmer switch to indicator lamp
Blue/White - Dimmer switch to long-range driving light switch
Blue/Red - Headlight low beams
Brown - Main feed from the battery. No switches or fuses
Brown/Yellow - GEN to volt. regulator
Brown/Blue - Power feed to headlamp switch
Brown/White - Ammeter to main alternator terminal
Brown/Yellow - Long-range driving light switch to lamp
Brown/Yellow - Alternator to 'no charge' warning light
Brown/Purple - Alternator regulator feed
Brown/Green - Fuse to horn (No relay)
Brown/Black - Horn to horn button (no relay)
Green - Ignition circuit, additional switches or fused
Green/Black - Fuel gauge to fuel tank unit
Green/Blue - Water temperature gauge to temperature sender unit
Green/Red - Direction indicator switch to left-hand flasher lamps
Green/Purple - Stop lamp switch to stop lamps
Green/White - Direction indicator switch to right hand flasher lamps
Green/Yellow - Heater switch to heater motor
Light green/Blue - Flasher switch to left-hand flasher warning light
Light green/Brown - Flasher switch to flasher unit
Light green/Purple - Flasher unit to flasher warning light
Purple - Accessories fed direct from battery via fuse
Purple/Brown - Horn fuse to horn relay when horn is fused separately
Purple/Red - Switches to map light, under bonnet light, glove box light and boot lamp when fed direct from battery fuse
Red - Tail lights, instrument lights and side markers
Red/Yellow - Fog light switch to fog light or fog light fuse to fog lights
Red/Blue - Front fog light fuse to fog light switch
Red/White - Fuse to instrument lamp switch, Instrument panel lamps
White - Ignition circuit, no additional switches, not fused
White - Power to coil
White/Black - Ignition coil to distributor
White/Brown - Oil pressure switch to warning light
White/Pink - Ignition switch to radio fuse
White/Red - Ignition switch or starter switch to starter solenoid
Yellow - Generator connections wired through the ignition switch
Yellow/Green - Dynamo 'F' to control box 'F' Alternator field 'F' to control box