Where to \definecolor?

Question

When I put color definitions in the preamble, I get an error, e.g.

\documentclass[12pt]{article}

\usepackage{xcolor}

\definecolor{es-bg}{HTML}{e7edf4ff}% (cornflower light blue background at the top)
\definecolor{es-aqua}{HTML}{00ffffff}% (bright aquaish, matches)
\definecolor{es-lb}{HTML}{0090d4ff}% (lighter blue, matches)
\definecolor{es-db}{HTML}{003b74ff}% (darker blue, matches)

\begin{document}


\colorbox{es-aqua}{This should be a color.}

\end{document}

gives an error of "Missing \begin{document}".

If I put the definitions after \begin{document}, it compiles but there is an extra line "FFFFFFFF" in the document, e.g.

\documentclass[12pt]{article}

\usepackage{xcolor}

\begin{document}
\definecolor{es-bg}{HTML}{e7edf4ff}% (cornflower light blue background at the top)
\definecolor{es-aqua}{HTML}{00ffffff}% (bright aquaish, matches)
\definecolor{es-lb}{HTML}{0090d4ff}% (lighter blue, matches)
\definecolor{es-db}{HTML}{003b74ff}% (darker blue, matches)

\colorbox{es-aqua}{This should be a color.}

\end{document}

Answer 1

It's completely fine to define colors in the preamble. But the HTML format asks for 6 numbers/letters, not 8:

\documentclass[]{article}

\usepackage{xcolor}
\definecolor{es-bg}{HTML}{0df400}

\begin{document}
\textcolor{es-bg}{Hello}

\end{document}

Answer 2

The xcolor HTML color model takes 6 uppercase hex digits so

\documentclass[12pt]{article}

\usepackage{xcolor}

\definecolor{es-bg}{HTML}{E7EDF4}% (cornflower light blue background at the top)
\definecolor{es-aqua}{HTML}{00FFFF}% (bright aquaish, matches)
\definecolor{es-lb}{HTML}{0090D4}% (lighter blue, matches)
\definecolor{es-db}{HTML}{003B74}% (darker blue, matches)

\begin{document}


\colorbox{es-aqua}{This should be a color.}

\end{document}