A good approach is to define your own "cycle list".
The cycle list controls which colors are assigned unless your explicitly overrule the cycle list:
\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{
cycle list={red\\yellow\\green\\},
}
\begin{document}
\begin{tikzpicture}
\begin{axis}
\addplot coordinates{(0,0) (1,2)};
\addplot coordinates{(0,1) (1,3)};
\end{axis}
\end{tikzpicture}
\end{document}
Here, the first plot has no arguments and uses the first entry of the current cycle list
(which is red
). The second plot uses the second entry of the cycle list
(which is yellow
).
This allows to define a global set of colors.
If the global cycle list
contains only one entry, all plots will use this entry.
At the same time, you can still overrule color definitions by writing \addplot[<customized>]
(which will ignore the cycle list entry) or \addplot+[<customized>]
which will still use the cycle list, but it will append the customized options.