Yeah IQ is right there dude, see;
Mixing any 2 colours together creates whatever colour is halfway between those colours. brown is closer to orange, so depending on how much red you threw in there, it's gona sway it more that way.
As for gravity, I think that has more to do with how much force gravity applies to the planet as a whole, rather than individual objects. The planet spins through space at what, 1000 mph? And it travels around the sun at around 67,000 mph. That's what causes gravity to make things stick to the surface with a determined amount of force, regardless of the mass of the object.