FYI:
In order, the stripes were:
None or Black Stripe
Purple Stripe
Red Stripe
Blue Stripe
Green Stripe
As with all things MESA, what these various stages represent are a matter of opinion with respect of the sound character. Don't let anyone pass on a bunch of bulls**t about one being better than the other. They represent snapshots in time of the development of an amplifier line. If the amplifier gets you the tone you want, the jiffy marker is nothing more than a mark of its vintage. Much anxiety is generated in the Mark III group by this extensive evolution, much because of misinformation about what these stripes represent.
#1 - No mark or a little dot. Only a few hundred then some balck marks or "+"'s .
- Lean and powerful amp with more output power than a IIC+
#2 - Purple: reshaping of R2
- R2 was shaped to be more "rounded" and less gain, with improved level
#3 - Red: R2 is like current Mark III
- R2 further developed and very hot. Lead mode is also tweaked to close in on the IIC+ sound
#4 - Blue: Reshaping of R1
- More aggressive preamp gain - reshaping of R1, Power section made akin to IIC+
#5 - Green/Simul-Class: Final R1 and Lead Channel reshaping
- Cleaner R1, Lead channel reshaping, and unlike other Simul amps, these Mark III's were wired in Pentode - NOT triode in the Class A sockets for more power. Power section is same as Blue otherwise