u/5-0-2_Sub

Both of them are definitely blue, that's no question. Rocky's white for the whole movie, but I think Grace builds up to it over time. Maybe they differ in Rocky having Green to Grace's red?

As for mechanics, I think both of them would be centered around one of abilities that let you see more of your deck (scry, surveil, explore, etc.) but through different means - Rocky tapping artifacts he creates (referencing his Xenonite puppet shows) and Grace either being exiled or (ironically) having Heroic.