In the main we use a double pole switch for outside lights, so if they get water in them we can switch them off, otherwise they may trip the RCD and stop you resetting it, so switch there so you can isolate either due to water ingress or to change bulb.
The normal colours are green/yellow earth, blue neutral, and brown line, but there is nothing forcing anyone to use those colours, so common to find blue is switched line.
jow69 You do not say what the picture is of, so I will have to assume it is the remains of the previous light fitting.
Since external lights often fail after a few years I would remove the "box" from the wall and install a wiska box or similar. Once completed you can then use said box as an external junction box (Wago connectors would also be useful) then when the new lamp fails (Sadly it will after some years) You can then install a new light with no fuss what so ever as you have already done the hard part.
Your new light should connect colour to colour, but without test equipment (Even a multi meter) there is no way to know which brown is permanent live or switched live.
it's was a new build 7yrs ago, which it have never had anything wired to it. the light with Sensor which I am fitting to it and as 2 wires brown and blue. just want to know which wires go where. one of maintenance lads at work told me brown to brown and blue to black with brown sleeve. BUT need a 2nd opinion
Looks like this has been wired with a permanent live & a switch live, (Brown wire x2) some security lights have the option for this. It can then be operated by the switch indoors or it will work with the sensor even if the switch inside has been turned off. you will need some test equipment to see which brown wire is the switch wire & which one is the permanent live. Make sure the power is turned off at the mains before attempting to fit a new light, as it may be still live even though the switch is off !!
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