I've searched and searched. I've PM'd a couple of people, but I still don't know.

What the heck are "Blue Motors"?
Are "blue motors" any better or worse than others?

they are mercury motors that are painted mercury blue, typically their HP stuff, for example, merc builds 502's. one is just a simple MPI, the other is the EFI, a little better motor, and painted blue

"blue motors" refer to Mercury Racing engines as they are usually blue compared to black Mercruiser engines. Now they come in different colors and combos, but still usually referred to as "blue motors"

It's usually a sign of value, reliability, etc.

I would much prefer "blue" motors over someone homebrew rebuilds.

Blue= better motor if it is a Mercury product. Better as in better internals and more horsepower per C.I.

hp500 carb
500 efi
500efi with Whipples still blue

does not make a difference if you are color blind !