\documentclass[pstricks]{standalone}
\usepackage{pst-node}
\usepackage{etoolbox}
\expandafter\patchcmd\csname @begindocumenthook\endcsname{\psset{fillcolor=white}}{}{}{}
\let\psnewstyle\newpsstyle
\let\psnode\pnode
\let\psrectangle\psframe
\psnewstyle{mystyle}
{
fillstyle=solid,
fillcolor=cyan,% does NOT affect pscustom
linewidth=2pt,
linecolor=red,
}
\psset{style=mystyle}
\begin{document}
\begin{pspicture}(3,3)
\pscustom{\psrectangle(1,1)(2,2)}
\psnode(1,2){A}
\psdots[linecolor=blue](A)