Effects and Sequences are declared like this:

Effect<ReferenceType, ValueType> myEffect = new Effect<RefrenceType, ValueType>();
Sequence<ReferenceType, ValueType> mySequence = new Sequence<RefrenceType, ValueType>();

 
This section is about the ReferenceType and the ValueType. These are both called template type arguments.

ReferenceType is the type of the Sequence.Reference variable. It can be the type of any class, struct, or variable. The type just has to match the type of the reference variable. It can even be a built in type, like int, but if you make it a built in type then you’re doing it wrong. If you’re leaving the Reference variable as null then make this type object. However, if you leave Reference as null then you’re also doing it wrong.

ValueType is the type of value that you are acting on. It can be float, double, Vector2, Vector3, Vector4, Rect, Color, or Quaternion. Whenever you see anything in these documents that says “function x passes a value” then that value is of type ValueType.

You can’t put effects in a sequence unless their template type arguments match. If you want to form a sequence that switches types you’ll have to make two separate sequences and chain them together using OnComplete.