In typescript, why is a union of enums not also an enum?

Question

I have two enums that I would like to union.

enum Color {
    RED = 'red',
    BLUE = 'blue',
}

enum Shape {
    CIRCLE = 'circle',
    SQUARE = 'square',
}

However when I declare a union type and attempt to reference a member:

type ColorShape = Color | Shape;
const test: ColorShape = ColorShape.RED;

I get a compile time error:

TS2693: 'ColorShape' only refers to a type, but is being used as a value here.

Why is this? Would an union of enums not also be an enum itself?