Nested data member pointer - not possible?

AFAIK, this is not possible. A pointer-to-member can only be formed by an expression of type &qualified_id, which is not your case.

Vite Falcon's solution is probably the most appropriate.

I assume you are trying to get the pointer to the datamember Red. Since this is defined in the struct Color the type of the pointer is Color::*. Hence your code should be:

int main() {
    float Color::* ParamToAnimate;
    ParamToAnimate = &Color::Red; 
    return 0; }

To use it, you need to bind it to an instance of Color for example:

void f(Color* p, float Color::* pParam)
{
    p->*pParam = 10.0;
}
int main() {
    float Color::* ParamToAnimate;
    ParamToAnimate = &Color::Red; 

    Material m;
    f(&m.DiffuseColor, ParamToAnimate);
    return 0;
}

EDIT: Is it not possible to make the animation function a template? For example:

template<class T>
void f(T* p, float T::* pParam)
{
    p->*pParam = 10.0;
}
int main() {

    Material m;

    f(&m.DiffuseColor, &Color::Red);
    f(&m, &Material::Brightness);
    return 0;
}