Conflict between Options of Packages

Question

I have these following packages defined in my preamble and once the file is ran, it creates an error of the following saying there is a clash within the package options. Packages are below:

\documentclass[addpoints,11pt]{exam}
\usepackage{mathtools}
\usepackage{amssymb}
\usepackage{latexsym}
\usepackage{enumerate}
\usepackage{array}
\usepackage{amsthm}
\usepackage{cancel}
\usepackage{amsfonts}
\usepackage{tikz}
\usepackage{upgreek}
\usepackage{calligra}
\usepackage{graphicx,graphics}
\usepackage[normalem]{ulem}
\usepackage[all]{xy}
\usepackage[dvipsnames]{xcolor}

\begin{document}
 .......    
\end{document}

Is there a way to prevent and what is the actual root of the problem to persist?

Answer 1

\PassOptionsToPackage{dvipsnames}{xcolor}
\documentclass{...}
\usepackage[normalem]{ulem}
\usepackage[all]{xy}
\usepackage{xcolor}

However, it looks like that xcolor is already loaded by your documentclass or another package

Answer 2

Well, since Herbert provide a general solution for option clash, here is another solution:

\usepackage[dvipsnames]{xcolor}
\usepackage{tikz}

Just put xcolor package before tikz package.

Explanation:

In LaTeX, you cannot load a package through \usepackage twice or more. If a package has been loaded, another \usepackage without any options will be safely ignored, but a \usepackage with some options will produce an option clash.

tikz package loads xcolor internally without any options. If you want to use xcolor with additional options, you can use it before tikz.

---

You can even use this way to prevent the option clash:

\documentclass[dvipsnames]{exam}
\usepackage{tikz}

Options for \documentclass are global. These options will be passed to any later packages if possible. It is especially useful if you want to pass an option to a package that loaded by the document class. However, it isn't as precise as \PassOptionsToPackage.

Answer 3

Running

\documentclass[10pt]{article}
\usepackage[normalem]{ulem}
\usepackage[all]{xy}
\usepackage[dvipsnames]{xcolor}
\begin{document}
abcdefgh
\end{document}

does not produce any warnings or errors on a current TeXlive 2011 installation.

If you are using additional packages (hyperref is one that this problem is seen with, for example) here may well be ways round the problem: for example, try using the xcolor svgnames option if that color range is appropriate, use explicit \definecolor commands or try various diagnostic procedures.

Providing more information, including a complete but minimal size working example of the problem would help provide better responses.