-The supported flags are {\bf wxC2S_NAME}, to obtain the colour
-name (e.g. wxColour(255,0,0) -> \texttt{``red"}), {\bf wxC2S_CSS_SYNTAX}, to obtain
-the colour in the \texttt{``rgb(r,g,b)"} syntax
-(e.g. wxColour(255,0,0) -> \texttt{``rgb(255,0,0)"}), and {\bf wxC2S_HTML_SYNTAX}, to obtain
-the colour as \texttt{``\#"} followed by 6 hexadecimal digits
-(e.g. wxColour(255,0,0) -> \texttt{``\#FF0000"}).
+The supported flags are \textbf{wxC2S\_NAME}, to obtain the colour name (e.g.
+wxColour(255,0,0) -> \texttt{``red"}), \textbf{wxC2S\_CSS\_SYNTAX}, to obtain
+the colour in the \texttt{``rgb(r,g,b)"} or \texttt{``rgba(r,g,b,a)"} syntax
+(e.g. wxColour(255,0,0,85) -> \texttt{``rgba(255,0,0,0.333)"}), and
+\textbf{wxC2S\_HTML\_SYNTAX}, to obtain the colour as \texttt{``\#"} followed
+by 6 hexadecimal digits (e.g. wxColour(255,0,0) -> \texttt{``\#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
+\textbf{wxC2S\_CSS\_SYNTAX} (which is the only one supporting alpha) is not
+specified in flags.