How can I redefine a starred LaTeX command that take parameters?

Question

I am trying to redefine \chapter command like this

\let\oldchapter\chapter
\renewcommand\chapter[1]{{\color{green!30!blue!80}\oldchapter{#1}}}

These instructions were working before I start using the starred version \chapter*, but now I get compilation errors. I have searched a lot and found some guides (like this one) and answers but I can't get my code to work. Please tell me how I can edit this code to make it work, I have seen a lot of examples but I couldn't figure the right way to redefine starred commands.

See [Defining starred versions of commands (* macro)](http://tex.stackexchange.com/q/4386/5764) — Werner, Jul 08 '16 at 16:02
This is an XY-problem. Your real question is: How can i have a coloure chapter title. — Johannes_B, Jul 24 '16 at 08:10

score 1 · Accepted Answer · answered Jul 08 '16 at 14:32

Finally, I have found the solution from this old topic. My working code is now :

\newcommand{\@chapterstar}[1]{{\color{green!30!blue!80}\oldchapter*{#1}}}
\newcommand{\@chapternostar}[1]{{\color{green!30!blue!80}\oldchapter{#1}}}
\renewcommand{\chapter}{\@ifstar{\@chapterstar}{\@chapternostar}}

How can I redefine a starred LaTeX command that take parameters?

1 Answers1