You will have probably noticed that many genuine RMC have a small (usually red) tab on the centre rear of the Yoke on the jeans, kinda looks similar to the type of thing you see on Levis jeans. Here are the genuine ones.
One thing they all have in common whatever jeans they are found on, is that the inside of the tab is aways the same colour as the outside of the tab. Bear in mind though that not all RMC's even have a tab on the rear, and to confuse things futher you can get two pairs of the same design, one will have a tab and the other wont. I think that is to identify which territory they were released in, in a similar way the laser numbers do.
There are 3 colours of tab, 1st up is Red, the most common an found on many RMC designs;
Next up is Black, not very common and seen on a very few designs, one example is the AAAA Like Black collab design;