how to draw a bicolor tcolorbox without frame?
You can use frame hidden
\documentclass{article}
\usepackage{lmodern}
\usepackage[most]{tcolorbox}
\begin{document}
\begin{tcblisting}{bicolor, colback=blue!15,
colbacklower=white, boxrule=0pt,frame hidden}
This is an example of a \emph{bicolor} \texttt{tcolorbox}
\end{tcblisting}
\end{document}
Not sure if this is what you wanted, but you can add \tcbset{colframe=white}
to your preamble (or locally).
Output
Code
\documentclass{article}
\usepackage{lmodern}
\usepackage[most,listings]{tcolorbox}
\tcbset{colframe=white}
\begin{document}
\begin{tcblisting}{bicolor, colback=blue!15,colbacklower=white, boxrule=0pt}
This is an example of a \emph{bicolor} \texttt{tcolorbox}
\end{tcblisting}
\end{document}