Take the light, that the switch controls down. See if the white one in the back of the box goes to it. If it does tie a new one on to it and pull it down to the switch, now you have enough to splice. Don't worry about the orange one, it is for a different circuit. Just remember to check the voltage. Most likely the conduit goes from the switch to the light. If not you may have to open a few more boxes to follow the wire. The High voltage scenario is very slim in a residential application.
If that wire is grey and not white then beware you may have a 277volt circuit. brown orange and yellow wires with Grey neutrals are supposed to be 277/ 480 volt colour code and black red blue and white are 120 /240 colour code. only until recently has this practice become mandatory and we electricians just did it for ourselves. Some guys did there Own thing, Which is what you probably have there.
I Hope this helps You too Knightrider. .
Grey is a neutral wire also
sometimes guys will use different colours just to make it easy to Identify