Sorry Jason for the "resin" nomenclature confusion. I work a lot in industry with plastics and to many in this industry any sort of polymer material is called a resin, whatever type or form it is.
Your parts did look 3D printed to me, I guessed by FDM based on the surface texture. I didn't know what filament you had used.
I have in fact seen black coloured slightly conductive PETG filament, made with carbon pigment (usually crushed coal or charcoal).
I have also seen non conductive black coloured NON conductive PETG filament made with chemical dyes rather than conductive pigments. As you said, uncoloured or light coloured PETG is non conductive, at least the clear/translucent, light blue, and white PETG filaments I have seen were.