[Tex/LaTex] Package xcolor Error: Undefined color `lightblue2′

color

I am getting this error when trying to compile a TeX document using pdflatex:

Package xcolor Error: Undefined color `lightblue2'

Here is my file:

\documentclass{article}
\usepackage[x11names, rgb]{xcolor}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{snakes,arrows,shapes}
\usepackage{amsmath}
%
%

%

%

\begin{document}
\pagestyle{empty}
%
%
%

\enlargethispage{100cm}
% Start of code
\begin{tikzpicture}[>=latex',line join=bevel,]
%%
\node (Wollongong) at (487bp,594bp) [draw=lightblue2,fill=lightblue2,ellipse] {Wollongong};
  \node (PDP-11 Sys V) at (884bp,306bp) [draw=lightblue2,fill=lightblue2,ellipse] {PDP-11 Sys V};
  \node (Interdata) at (258bp,594bp) [draw=lightblue2,fill=lightblue2,ellipse] {Interdata};
  \node (2*8 BSD) at (221bp,162bp) [draw=lightblue2,fill=lightblue2,ellipse] {2.8 BSD};
% CODE REMOVED TO SAVE SPACE
%
\end{tikzpicture}
% End of code

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\end{document}
%

Best Answer

You are looking for the colour LightBlue2, not lightblue2.

Internally all colours are represented as macros and, macros are case-sensitive. That is, \latex is different from \Latex and \LaTeX and \LATEX and... In fact colour X is stored in a macro \\color@X:

enter image description here

\documentclass{article}
\usepackage[x11names]{xcolor}
\begin{document}
\textcolor{LightBlue2}{something}

\makeatletter
\ttfamily\verb|\\color@LightBlue2|:
\expandafter\expandafter\expandafter\strip@prefix\expandafter\meaning\csname \string\color@LightBlue2\endcsname
\end{document}
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