As I said, with pipe I use anything that isn't already used and that's acceptable as a phase. The full list of (easily available) phase colours in Austria is:
- black
- brown
- grey
- white
- orange
- purple
The first three are the official recommendation for phases (L1 brown, L2 black, L3 grey) but can be used differently. In domestic conduit jobs I frequently see 3 black phases. Red is in theory an acceptable phase colour too but frowned upon because it used to be earth (ground) until 1965. Many electricians will even tell you that red may not be used for mains wiring at all and red earths have to be replaced as soon as you touch the wiring. Of course that's not correct but many strongly believe in that theory. Yellow and green are available but explicitly not to be used outside factory-wired equipment because either could be confused with yellow/green.
Probably the most common colours for switch legs, travellers and other non-standard stuff (e.g. control wiring from push-buttons to 230 V operated latching relays, which are highly popular whenever a light is to be switched from more than two points, most sparks won't do 4-ways unless specifically told to) are orange and purple. Most contractors I've experienced will only have black, blue, yellow/green, orange and purple 1.5 mm2 in their vans, larger sizes only as required and usually only the first three plus brown 6 and 10 mm2 (required for load side meter tails).
