plc wire colour and e-stop safty

whatis the standard colour wire for wiring a plc to other circuits in canada . would
it be ok to use the following if it is documented in the wiring diagram.
inputs : orange outputs : purple
0 volts : blue 24 volt : brown

In an E-Stop condition I need to maintain pwr to the plc ,can I take the power supply through a breaker before the main contactor and cut off the 24v comm to the output of the plc. what colour should I use from the safty relay to the plc if the common is 24v (pnp)I was using yellow from the relay and yellow for the common .
also if the plc is (npn) what colour should I use
for the output common
thanks

this site is great learning a lot

Most wire color coding is done based voltage level, not by whether the wire is an input or output. You can get some guidance on this thread:

http://www.plctalk.net/qanda/showthread.php?s=&threadid=1415&highlight=wire+color

Simialr info is on this one:

http://www.plctalk.net/qanda/showthread.php?s=&threadid=369&highlight=wire+color

While were on the subject.

Does anyone know where I can obtain a copy of the NFPA 79 on CD? I have the 2002 NEC on CD but I can't seem to find anyone that has the 79.

Straight from NFPA http://www.nfpa.org/

This is a rough guide I go by. I don't know if its a true standard but it is most accepted by the customers that I have delt with in Canada and US.
Black- Line and load circuits AC or DC above 150 volts
Red- AC control circuits 150 volts and lower
Blue- DC control circuits 150 volts and lower
Yellow- All control circuits or wiring that remains energized when the main disconect is off.
There are more but those are the most important.

Wiring Standards in my plant -

Control circuit voltages and permitted colors.
12 VAC, hot leg - Orange
12 VAC, return leg - Orange with White stripe
24 VDC, positive - Blue
24 VDC, negative - Blue with White stripe
120 VAC, hot leg - Red
120 VAC, return leg - White with Red stripe
120 VAC, return leg - Switched - Red with White stripe
Dedicated - Isolated circuits - Purple

Single phase power circuit voltages and permitted colors.
240 VAC, A phase - Black
240 VAC, B phase - Red
120 VAC, return leg - White

Three phase power circuit voltages and permitted colors.
208 VAC, A phase - Black
208 VAC, B phase - Red
208 VAC, C phase - Blue
120 VAC, return leg - White

240 VAC, A phase - Black
240 VAC, B phase - Red
240 VAC, C phase - Blue
120 VAC, return leg - White

480 VAC, A phase - Brown
480 VAC, B phase - Orange
480 VAC, C phase - Yellow
277 VAC, return leg - White

E_Stop circuit

typically, the E_Stop circuit is hard wired to a coil on the Master Control Relay(MCR) or Master Safety Relay( typically a power relay as opposed to a control relay). Then the Output Power to either hardwired devices or a PLC output board are wired through the contacts of this relay