Russian military aircraft have no real registrations, I assume the construction number is used instead.
The numbers painted on the aircraft typically only identifiy an aircraft within a unit, so they are really codes, but they are used as the registration on Airliners.net for lack of anything else.
Different squadrons within a regiment (wing) use different colours, so the colour is significant. This is why plane spotters traditionally note the colour, and why A.net wants Russian military aircraft listed like this.
However, few people know about this, and also the desired format is not clear. One of the editors showed me the offical rule and it says the format should be 1 white (no capitals), however if you upload this way screeners will often change this to 1 WHITE.
It's a bit messy, and maybe it would be better to get rid of this.