Wire Color Code

I have been reading the past posts about color coding standard.
I cannot
understand why you would use Blue as DC+ and Wht/Blue as 0VDC
when the manufacttures on all their sensors use BROWN +24VDC
BLUE-0VDC and black as the switch. Can someone explain this to me.

A lot depends on company standards.

One of the big corporations that I did a lot of work for used brown for jumpers only.

Their projects may have 10 or more colors for 24vdc.

I came up with the idea of using an Excel speadsheet for the numbers, which I could sort by number, location, etc. Also, with Excel, I could color code the "line" and make it match the color of the wire.

Obviously, white was a problem, and yellow was sometimes hard to read.

With 24vdc, there is no "LAW".

regards.....casey

Especially recently, manufacturers design sensors that have a range of operating voltages and use QD style connectors. Blue has been used to signify 24V and red 120 but what color wire should I use if I build a sensor that can handle both voltages?

My latest controls systems uses Allen-Bradley QDs that have all red wires with different tracers but the controls on the ends of those QDs are 24VDC (with blue wires from the panel...).

Brown/Blue is the European color code -

Brown indicates the hot line, blue indicates the neutral line. Its seems to be used on both AC and DC systems.