\definecolor{cas}{HTML}{e6f0fe}
\definecolor{important}{HTML}{fc9871}
\definecolor{dark-gray}{gray}{0.2}
-\definecolor{orange}{HTML}{e6beb2}
+\definecolor{peach}{HTML}{e6beb2}
\definecolor{lblue}{HTML}{e5e9f0}
\newtcolorbox{cas}{colframe=cas!75!black, title=On CAS, left*=3mm}