This is confusing because different fourth brake lights use different wire colors. However, I did something like this.
Anyways, with my best guess, Green, Red, Black, Yellow. Red and black obviously is the power and ground for what your brake triggers. Green is your reverse light because i think thats what the color of the plug is. But you can make sure to see what wire it goes to. Yellow is probably your flasher.
Anyways, to wire it, you need the brake wire and another wire connected to the flasher like the picture above. The reverse wire should be soldered on the reverse. (Again, reverse and reverse ground should be on your harness to plug up. Might need to repin to match colors accordingly. Red wire assuming its your brake wire needs to be spliced into your tail light's brake wire to stay lit. In the pic, the strobe and brake light are soldered together so both would get the power source from when you brake. lmk if this helps, its hard figuring this out without being there or seeing it. I've done this three times before but it was years ago.