Fancy example environment

Question

How do create a colourful example environment like the one here?

Answer 1

Below I present two options, both of them admitting page breaks.

1. A simple example using tcolorbox (admits page breaks); adjust the settings according to your needs:

   

   The code:

   \documentclass{article}
   \usepackage{lipsum}
   \usepackage[many]{tcolorbox}
   
   \definecolor{greentitle}{RGB}{61,170,61}
   \definecolor{greentitleback}{RGB}{216,233,213}
   
   \newtcolorbox[
     auto counter,
     number within=section
   ]{myexample}[2][]{%
     breakable,
     enhanced,
     colback=white,
     colbacktitle=white,
     arc=0pt,
     leftrule=1pt,
     rightrule=0pt,
     toprule=0pt,
     bottomrule=0pt,
     titlerule=0pt,
     colframe=greentitleback,
     fonttitle=\normalcolor,
     overlay={
       \node[
         outer sep=0pt,
         anchor=east,
         text width=2.5cm,
         minimum height=4ex,
         fill=greentitleback,
         font=\color{greentitle}\sffamily\scshape
       ] at (title.west) {example~\thetcbcounter};
     },
     title=#2,
     #1
   }
   \newcommand\Solution{\par\textbf{\textsf{Solution}}\par\medskip}
   
   \begin{document}
   
   \section{A test section}
   \begin{myexample}{Factorise $x^2-2x+1$}
   \Solution
    \lipsum[4]
   \end{myexample}
   
   \end{document}
   

2. A simple example using mdframed (admits page breaks); adjust the settings according to your needs:

   

   The code:

   \documentclass{article}
   \usepackage{chngcntr}
   \usepackage[tikz]{mdframed}
   \usepackage{lipsum}
   
   \definecolor{greentitle}{RGB}{61,170,61}
   \definecolor{greentitleback}{RGB}{216,233,213}
   
   \newcounter{mdexample}
   \counterwithin{mdexample}{section}
   
   \newenvironment{myexample}[1]
     {\stepcounter{mdexample}\begin{mdframed}[
       frametitle=#1,
       frametitlefont=\normalfont,
       topline=false,
       bottomline=false,
       rightline=false,
       linecolor=greentitleback,
       linewidth=2pt,
       singleextra={
         \node[
           overlay,
           outer sep=0pt,
           anchor=north east,
           text width=2.5cm,
           minimum height=4ex,
           fill=greentitleback,
           font=\color{greentitle}\sffamily\scshape
         ] at (O|-P) {example~\themdexample};
         },
       firstextra={
         \node[
           overlay,
           outer sep=0pt,
           anchor=north east,
           text width=2.5cm,
           minimum height=4ex,
           fill=greentitleback,
           font=\color{greentitle}\sffamily\scshape
         ] at (O|-P) {example~\themdexample};
         }
       ]
     }
     {\end{mdframed}}
   \newcommand\Solution{\par\textbf{\textsf{Solution}}\par\medskip}
   
   \begin{document}
   
   \section{A test section}
   \begin{myexample}{Factorise $x^2-2x+1$}
   \Solution
    \lipsum[4]
   \end{myexample}
   
   \end{document}