The spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid part of its cost.

The spell checks on resolution to see if any mana of the stated colors was spent to pay its cost. If so, it doesn't matter how much mana of that color was spent.

If the spell is copied, the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.

When you cast the spell, you choose its targets before you pay for it.

You choose whether or not to target a creature spell before you decide whether or not to spend on Repel Intruders. You may target a creature spell and then not spend to cast Repel Intruders; if you do, Repel Intruders simply won't affect that creature spell. Similarly, if you don't target a creature spell but then you spend to cast Repel Intruders, that part of Repel Intruders has no effect.

If you choose to target a creature spell, Repel Intruders has a target. If that target becomes illegal by the time Repel Intruders resolves, the entire spell will be countered. You won't get any tokens.