I'm installing a 240V/60A SPA approximately 85 feet from the house service panel. I'm going to run 3 individual #6 conductors (THN or better) from the service panel to the SPA GFI disconnect box via 1 inch PVC conduit. The SPA is about 7 feet from the disconnect box. The disconnect box instructions suggest that a separate grounding wire from the service panel to the disconnect box is not necessary.---TRUE?
If not true, will a single #10 insulated conductor suffice ar does it have to be the same gauge as the #6 powered conductors? Does the insulation have to be green?

A #10 green wire is needed as an equipment ground from the panel to the spa pulled in the conduit with the feeder conductors.