For my 3 hunter boxing, I assigned the assist fellowship as Ctrl + ` (tilda), for the color contribution I set ` (tilda) to the specific color for each char, not as versatile, but pretty consistent and reliable.

So when a FM is triggered, I hit Ctrl + tilda, now all toons are targeting Mains target directly, then ` (tilda) to contribute colors at same time, Then F2 or my F2, /follow macro to reacquire main as target. I have noticed if you press the fellowship assist twice it will lose target and pressing fellowship assist again will not target correctly, so careful not to double broadcast the mapped key for assit fellowship.

Also I recomend not setting the fellowship assist for your main to the same as your followers. I prefer to manually use the Assist Fellowship target icon with mouse, or at least to another key press, not broadcast to followers.

I was playing with 3 color straights, but getting correct order less then 100% of the time, so switched to main doing any color of choice and followers doing 2 color combos.

Notes for my set up, I use Ctrl and Alt as modifiers keys for diff hotbars, so my mouse thumb buttons are programed as Ctrl and Alt for fast presses without moving my left hand from number line on KB, so ctrl+Tilda is very easy and quick to execute.

I like using the direction keys for FM when solo playing, but find them very useful for movement when multi boxing, I do not broadcast WASD movement keys to followers, and use to control main, but use the direction keys for breaking follow and positioning in combat of followers.