Redefine \citet command (two optional arguments case)

Question

I need to redefine "\citet" command to have its output printed in red. I did:

\let\oldcitet\citet
\renewcommand*\citet[2][]{{\color{red}\oldcitet[#1]{#2}}}

that works for the "one optional argument" case: \citet[ARG]{label}.

How can I get the same result for the "two optional argument" case: \citet[ARG1][ARG2]{label}?

Answer 1

You don't have to check for any optional argument, if you use the #1#{ argument to get everything before the {:

\let\oldcitet\citet
\def\citet#1#{\citetaux{#1}}
\newcommand*\citetaux[2]{{\color{red}\oldcitet#1{#2}}}