That may be a function of when the panel was wired. I don't know when the current marking rule came into effect.
In code, the wire with insulation that is commonly green is called an equipment ground
ing conductor. The the wire with insulation that is commonly white is called a ground
ed conductor.
https://www.ecmweb.com/national-ele.../code-qa-identification-of-circuit-conductors says
The neutral conductor of a branch circuit must be identified in accordance with 200.6 [210.5(A)]. Equipment grounding conductors can be bare, covered, or insulated. Insulated equipment grounding conductors size 6 AWG and smaller must have a continuous outer finish either green or green with one or more yellow stripes, in conformance with 250.119 [210.5(B)]. On equipment grounding conductors 4 AWG and larger, insulation can be permanently reidentified with green marking at the time of installation at every point where the conductor is accessible [250.119(A)].
So if that were #4 AWG, it could be OK.