The usual response to this is to use a family, so it would be Red overlaps with Family where the Family is also the Red object, but for picking purposes it means you can use Family for the first ball and Red for the second.
There is also something under system called pick nth instance where 0 and 1 would be the two instances in the collision, problem here is I'm not sure how it differentiates either one (could be IID). If it doesn't matter which is 0 and 1 then this could be a method you can use.