color: can be constructed via predefine ray's colors

lib/Ray/include/Color.hpp

@@ -20,6 +20,10 @@ namespace Ray {
             //! @param a A-component of color
             Color(unsigned char r, unsigned char g, unsigned char b, unsigned char a);
 
+            //! @brief A constructor using ray's own color struct
+            //! @info Useful when want to use pre-defined color
+            Color(const ::Color &);
+
             //! @brief A default copy constructor
             Color(const Color &) = default;