Method use

tutorials/external/catch.hpp:8315–8318

    Colour::~Colour(){ if( !m_moved ) use( None ); }

    void Colour::use( Code _colourCode ) {
        static IColourImpl* impl = platformColourInstance();
        impl->use( _colourCode );
    }

    std::ostream& operator << ( std::ostream& os, Colour const& ) {
        return os;