\documentclass[border=5pt]{standalone}
\usepackage{bytefield}
\usepackage{graphicx}
\usepackage{graphics}
\usepackage{xcolor}
\usepackage{subcaption}
\begin{document}
\definecolor{lightcyan}{rgb}{0.84,1,1}
\definecolor{lightgreen}{rgb}{0.64,1,0.71}
\newcommand{\colorbitbox}[3]{%
	\rlap{\bitbox{#2}{\color{#1}\rule{\width}{\height}}}%
	\bitbox{#2}{#3}}
	\begin{bytefield}[bitwidth=2pt,bitheight=\widthof{~Sign~},
		boxformatting={\centering\small}]{64}
		\bitheader[endianness=big]{63,13,0} \\
		\colorbitbox{lightcyan}{50}{VPN} &
		\colorbitbox{lightgreen}{14}{Page Offset}
	\end{bytefield} \hfill \break \newline

\definecolor{lightsomething}{rgb}{0.84,0.7,0.7}
\definecolor{lightsomething2}{rgb}{0.64,0.5,0.71}
	\begin{bytefield}[bitwidth=2pt,bitheight=\widthof{~Sign~},
	boxformatting={\centering\small}]{40}
	\bitheader[endianness=big]{39,13,0} \\
	\colorbitbox{lightsomething}{26}{FPN} &
	\colorbitbox{lightsomething2}{14}{Frame Offset}
\end{bytefield}

\end{document}