More on the line "If a egg Natty in a the red {Natty Dread}"
I 'sussed out' that meaning from the expressions 'to egg someone on' and the expression 'to see red'.
Btw, I don't think that 'suss' is commonly used in African American {that is non-Caribbean African American* conversations & writing. I'm wondering if it is common in the Uk, Canada, and/or Australia?
To infer or discover; figure out: "I think I'm good at sussing out what's going on" (Ry Cooder). To size up; study: "Suss out the designers in whom you are interested" (Lucia van der Post).
[Probably short for SUSPECT.]"
I suspect that suspect might be the origin of suss if you figure that you are checking something out to see if what you suspect is real and not a "fig newton" ** of your imagination.
** "fig newton"="figment" [That's just me playing with words. If you like it, be my guest and pass it on]
Fwiw, rhe word 'suss' isn't listed in the Rasta/Jamaican Dictionary whose link I provided earlier.
That same Rasta/Jamaican Dictionary doesn't give any meaning of natty as a stand alone word. Here's the nearest entry that they have:
NATTY, NATTY DREAD, NATTY CONGO: 1. dreadlocks 2. a person with dreadlocks