Dark colors will be hotter than light ones. It is physics. Take the temperature of each color on the side of your coach and you will find that the dark colors are considerably hotter than the light ones. How much the extra heat on the outside of your coach will affect the inside temperature is based on how well your coach is insulated. However, there will always be heat transfer from the skin of the coach to the inside, so a dark coach will be hotter and will require more AC to keep it cool. How much more is a question that cannot be answered without knowing the coach.
When we got our coach repainted, we chose much lighter colors so the coach stays cooler and so the paint lasts longer.
