This is from Miles Rose:
Mesa vs Groove Tubes scale
Red = 4
Yellow =4
Green =5
Gray =5
Blue =6
White =6
Mesa Red tubes are around 20mA (Ive seen as low as 12mA and high as 25mA). As each color change occurs, there is a 5-10mA increase. So a yellow would be 25-30mA, Green would be 35-40, etc. Keep in mind, as I mentioned earlier, the ratings can be off around 7mA (or more).
That said, there will be a tonal difference as well. The Greys will be in simple terms, hotter. So the amp will sound warmer mushier.
For those with simul-class amps. The outside simul sockets (or inside for Coli) will run hotter, so I suggest never going above red or yellow rating or those tubes will wear faster.
This is what I found based on having a shit load of mesa tubes and maxi-matcher tube testers.