You could use a continuity tester to check the plug positions on the old plug (back to thee junction box) and then transfer the plug pin in the new connectore. I would also leave a sheet with the new color code in the junction box for the future.
The list you have posted is correct for a standard 7 way plug connection. The black is a direct line to the trailer batteries for charging, and yes the blue is the brakes. The yellow will not be used if your trailer doesn't have backup lights. (mine doesn't)
Ah yes! You were all correct. I did find the wiring schematic on the truck plug and matched it up to the "continuity tested" trailer wires....Don't forget to disconnect the battery so when you have all those wires bared and they start touching each other...you don't get the back feed...My Bad!