Is there a requirement in the NEC regarding color for the bonding jumpers connecting all the grounding electrodes? Example, if using insolated cables as bonding jumper , do they need to be green?
There is no color code requirement for the GEC. There are some colors it shouldn't be, such as white or gray. Black or bare is safe, you could even use red, it wouldn't be a NEC violation, but the AHJ may not like it.