This union represents four color values which is usually used to store border colors.

You can find more information in comments below.

union RectC
    {
        struct
        {
            Color Left;
            Color Top;
            Color Right;
            Color Bottom;
        };
        Color Data[4];

        const Color &operator[](const int index) const; // Return element
        Color &operator[](const int index); // Return element
    };

Following operators are also available.

bool operator==(const RectC &a, const RectC &b); // Check if rects are equal
    bool operator!=(const RectC &a, const RectC &b); // Check if rects are not equal
    std::wostream &operator<<(std::wostream &stream, const RectC &a); // Output as source code