bulb earth please which is it

[wellskint]

i have an earth problem to the nearside headlight causing it to be dim. a i have cleaned up and replaced what wiring earths i can find on the body to no avail. please can somebody tell me which of the 3 terminals on the bulb connector is the earth - there are 2 wires that are red with bits of blue on and one that is black with bits of red on? and the earth is??????????????

 

[frank]

just test it with a meter or testlamp

 

[wellskint]

i have no equipment!

 

[frank]

http://www.ebay.co.uk/itm/CAR-VAN-A...228?pt=LH_DefaultDomain_3&hash=item3f434a115c £2.70 posted, might save you a load of grief