\definecolor{foldblue}{HTML}{2B5E8E}
\definecolor{foldorange}{HTML}{B65731}
\definecolor{foldgray}{HTML}{8B9399}
\definecolor{foldgreen}{HTML}{427E70}
\tikzset{
  fold edge/.style={draw=foldgray!80,line width=.75pt,line cap=round},
  marked edge/.style={draw=foldorange,line width=2.1pt,line cap=round},
  mirror/.style={draw=foldblue!55,dashed,line width=.75pt},
  part A/.style={circle,draw=foldblue,fill=foldblue,inner sep=0pt,minimum size=4.5pt},
  part B/.style={circle,draw=foldblue,fill=white,inner sep=0pt,minimum size=4.5pt},
  diagram label/.style={font=\small},
  diagram arrow/.style={-{Stealth[length=4pt,width=3pt]},line width=.8pt,draw=foldblue},
}