Returns a textual specification of @color in the hexadecimal form
<literal>#rrrrggggbbbb</literal>, where <literal>r</literal>,
<literal>g</literal> and <literal>b</literal> are hex digits representing
the red, green, and blue components respectively.
Return: a newly-allocated text string that must be freed with g_free().
Returns a textual specification of @color in the hexadecimal form <literal>#rrrrggggbbbb</literal>, where <literal>r</literal>, <literal>g</literal> and <literal>b</literal> are hex digits representing the red, green, and blue components respectively.
Return: a newly-allocated text string that must be freed with g_free().