Depending on how it was finished, G10 can have a bit of surface porosity compared to Zytel. Zytel is molded into net shape under heat and pressure. It should have zero surface porosity if it is molded correctly. The surface of G10 is sometimes sanded, which can leave the surface with micro-scratches, that is to say, someplace that the dye molecules can hang onto for a spell.
However, my expectation would be that, over time with continued usage, the color imparted by dying either G10 or Zytel will rub off. It might last a few weeks as an EDC before losing its color, perhaps longer if you don't really use the knife. I suppose it could last for years if you left it on the dresser. I would not expect it to last 6 months of daily usage where you really handle the knife. I've not tried it, but that would be my expectation for those materials.