+ Converts this colour to a wxString using the given flags.
+
+ The supported flags are wxC2S_NAME, to obtain the colour name (e.g.
+ wxColour(255,0,0) == "red"), wxC2S_CSS_SYNTAX, to obtain the colour in
+ the "rgb(r,g,b)" or "rgba(r,g,b,a)" syntax (e.g.
+ wxColour(255,0,0,85) == "rgba(255,0,0,0.333)"), and wxC2S_HTML_SYNTAX,
+ to obtain the colour as "#" followed by 6 hexadecimal digits (e.g.
+ wxColour(255,0,0) == "#FF0000").
+
+ This function never fails and always returns a non-empty string but
+ asserts if the colour has alpha channel (i.e. is non opaque) but
+ wxC2S_CSS_SYNTAX (which is the only one supporting alpha) is not