Hybrid Characters, Gaining Additional Powers (PHB3 p135):
[…] However, if you have at least two poweers in the same category (at-will attack, encounter attack, daily attack, or utility), at least one of those powers must come from each of your hybrid classes.
Gaining and Using a Skill Power (PHB3 p164):
[…] Whenever you reach a level that grants you a utility power from your class, you can choose a skill power in place of a class power […]
Specific over general does not help here, as both are equally general (or specific).
If we go by the first, you need to have at least 1 from each of your classes, so only your third can be anything else, if by the second, any of your utilities can be a sill power.
Which is it? Can I take a Skill Power before level 10 with a hybrid character?