Electrical – Light fixture earthing wires

Wiring colour conventions can vary worldwide, so as you don't state where you are located, it's not possible to give a definitive answer.

In the UK for example (for single phase wiring), convention would have the live wire as brown (new colour) or red (old colour) and the neutral wire as blue (new colour) or black (old colour). It was not uncommon to see appliances using the new colours while fixed wiring still used the old colours, until the new colour scheme was adopted for fixed wiring (around 2004).

If you are in any doubt at all, sound advice would be to contact a competent electrician to do the work for you.

Most likely you connect blue to blue, and brown to red or brown.

BUT you should really test it with voltage and continuity tester to be 100% sure you're connecting outside thread of a bulb to neutral and the pin to live.

How I understand colours of your wiring at the ceiling:

1. green/yellow: ground
2. blue: neutral
3. red: circut 1 live
4. brown: circuit 2 live

I assumed you have 2 switches on the wall. If you have just one switch, then possibly one of the live wires is not connected at all OR the opposite: it's permanently connected (for remote-controlled lamps).

And wiring on the fixture:

1. blue: bulb thread (must be connected to neutral)
2. brown: bulb base (must be connected to live)
3. metal thingy - if your fixture has extra screw that's simply connected to the metal body of the lamp, this is where the yellow-green ground wire goes)

About the testing you should do: With a neon probe on the wires coming from the ceiling: turn both switches "on" and verify which wires are live. Turn the switches off (or even better, ask someone to keep cycling one of them) to verify if they switch off properly and which switch is which circuit. With a continuity tester (eg. ohmmeter or a buzzer) on a disconnected fixture: check if blue goes to thread and if brown goes to base. Sometimes you can disassemble the fixture a tiny bit to simply see where the wires go.