Here is a comprehensive answer for your delectation.
The title of your post is 'What is RLM 02'. RLM stands for Reichsluftfahrtministerium which is German for "Reich Aviation Ministry'' 02 was just the colour number. As for what the colour looks like, your best bet is to look at the real thing and try to mix your own if you dont want to buy the right colour,
this colour isnt a bad representation of it but the plane is restored and they dont always get it spot on,
the wheel well picture is a much better match for the RLM 02 that i try to represent.
Be carefull with the JU88 though as the 1/32 one from revell was modelled on U4+TK that was salvaged from the depths of a norwegian Fjord in remarkably great condition. The surprise to a lot of modellers was that the cockpit was in great condition and RLM66 not 02 as most people would have thought for an early Luftwaffe plane. Here is a pic of the cockpit from the restoration teams website http://www.ju88.net/,
So, i hope your suitably confused LOL. Luftwaffe subject are great arnt they?
...Guy