7.62 NATO tip colors

Can anyone provide more information on the following US and Australian 7.62x51 cartridges?
(+) FA 57
Br cs and pr, yellow bullet tip - doesn’t appear to be either an observation or tracer round by x-ray examination.

(+) MF L2A2 61
Br cs and pr, purple annulus, dark green bullet tip, jacket cannulure, neck crimp - doesn’t look to be reload. A previous owner has labeled the cartridge as an experimental tracer. I have confirmed that it is a tracer by x-ray.

Dave S

Your green tipped Aussie cartridge would appear to be an experimental tracer
only manufactured in 1961. Possibility of having a US manufactured projectile.

As for the yellow tipped 7.62 I have no idea