On the first approach ColorOp{Color: red} would have to be boxed and thus heap allocated. This is because ops.Add in general would receive a (fat) pointer to a

On the first approach ColorOp{Color: red} would have to be boxed and thus heap allocated. This is because ops.Add in general would receive a (fat) pointer to a value implementing a particular interface rather than a value of concrete type. (The sibling comment written at the same time has a more detailed explanation of the 'fat' part.)