In theory, the red stripe denotes a Mercury designed for freshwater while the blue stripe denotes a Mercury designed for saltwater. But, since the parts are identcal in both it was just a marketing ploy.
I was referring to the S T R I P P E D Mercury engines, not the banded ones. I don't know when Mercury started the two different decal types, but I 'm sure they were still doing it up until at least 2004d