Warn uses them for thier disconnet plugs but they have keyed theirs so that you can only mate two Warn plugs together.
The colour is supposed to indicate the voltage used. A Red (24volt) plug can't be connected to a Gray (36volt) plug for that reason.
Warn chose red (24Volt) for some reason rather than Yellow which is correct for 12 Volts. Gray is very common because a lot of forklifts use 36Volts and that is where this technology was born. In my business (telecom) we use blue connectors for our 48 volt systems.
Anderson created a good system. If everything is wired correctly you should be able to connect any connectors that fit together and know that you have compatible voltages and current capacities. You should also be able to quickly tell by color and size what the voltage and current will be.
Unfortunately there are guys like me out there with a combination of blue and gray connectors on their rigs running 12 and 24 volt systems. A standard is only good if it is implemented.