The comments are pretty interesting and will this thing eventually take us to Mars?

Commenter Jon Yang had this to say:

Around 4:15 the plume starts to go from blue to red, anyone know why?  Change in the fuel/oxidizer mix? Heat of exhaust catching up the cooling ability of the engine bell?  Video illusion?

Commenter okantokyo had this to say about the test:

RS-25 needs to be requalified for the new loads in the SLS design.  The taller tank equals a different head pressure for these engines and so they have to be tweaked slightly to deal with the increase in pressure and flow rate.  Additionally, they’re using the J2X controllers instead of the legacy RS-25 computer system since its cheaper and more suited for a disposable rocket.   The real event though would be ordering RS-25-E as a full-up expendable variant, but who knows.

Very interesting stuff and I am looking forward to more research into this particular launch system!

thanks to NASA for the great info