After I updated texlive today, I noticed that \pagecolor from xcolor no longer works as it should. I tested this with lualatex, xelatex and pdflatex, but only xelatex gave the expected result (dark pagecolor). Here is an MWE
\documentclass{article}
\usepackage{xcolor}
\usepackage{lipsum}
\definecolor{Pagecolor}{RGB}{18,18,18} % Dark gray
\definecolor{Textcolor}{RGB}{225,225,225} % Light gray
\pagecolor{Pagecolor}
\color{Textcolor}
\begin{document}
\lipsum
\end{document}

\AddToHook{shipout/background}{\relax}to your document as a work around until I updated. – Ulrike Fischer Oct 04 '20 at 10:29