\documentclass[a4paper]{scrartcl}
\usepackage[utf8]{inputenc}

\usepackage{xcolor}

\definecolor{foo}{HTML}{EFF5F9}
\definecolor{magenta}{HTML}{FF00FF}

\begin{document}
    This is the \textcolor{foo}{foo color}. And here is an
    \textcolor[HTML]{DFECF7}{inline example}.

    I like \textcolor{magenta}{\textbf{Magenta}}.
\end{document}