How to change the opacity and height of border in tcolorbox?

Question

What I have:

I have the following code

\newtcolorbox{DefinitionBlue}{
enhanced,
fonttitle=\sffamily\bfseries,
coltitle=my-blue-2,
boxrule=0pt,frame hidden,
borderline west={5pt}{0pt}{my-blue-2},
opacityback=0
}

and in the document

\begin{DefinitionBlue}
This is a test
\end{DefinitionBlue}

which produces the following output

(note that I have set the background to be like this in the whole document; it is not a result of the colorbox)

What I want to do:

I want to create a highlighter effect (as if I have highlighted before the text), that is, I want the border to have lower opacity and I want to be able to change the height of the border. I have tried using the highlighter command, however, it is not flexible enough for me.

Can someone help me change the opacity and height of the border?

Thank you in advance.

Answer 1

The first argument is the border width, the second one is a shift and the third one is a list of options.

borderline west={10pt}{5pt}{blue, opacity=0.5}

To reduce the height we need an other approach:

\documentclass{article}

\usepackage[most]{tcolorbox}

\newtcolorbox{DefinitionBlue}{
enhanced,
fonttitle=\sffamily\bfseries,
coltitle=blue,
boxrule=0pt,frame hidden,
left=5mm,
%borderline west={10pt}{5pt}{blue,opacity=0.5},
overlay={
      \draw[line width=10pt,blue,opacity=0.5]
          ([shift={(3mm,-2mm)}]interior.north west)
          --([shift={(3mm,2mm)}]interior.south west);
        }
}


\begin{document}
\noindent
zrzer rzerz 
\begin{DefinitionBlue}
This is a test\\
Thid is as test\\
This is as test

\end{DefinitionBlue}
\noindent
dzaez zzrze
\end{document}