RLM 02 is described as a grey with some green in it. This same colour was also used on the exterior as the lighter shade for the two tone camouflage of 1940, so going straight grey won't be correct either.
I found this colour swatch, which I think is fairly accurate:
I haven't come across any negative reviews for Vallejo's shade, though one modeller did make the comment that:
t's the wierdest colour; looks grey when viewed next to green, green next to gray and brown in the bottle.
I've also read there was more than one company producing paints for the Luftwaffe, so there would be some variance. It's possible the bottle of Vallejo you have is a victim of the above occurrence, in that the colour is a bit off? You can also try taking the eyedropper off the top so you an get a stir stick in there just in case shaking wasn't enough.
regards,
Jack