pgfkeys Error: I do not know the key '/tikz/green '

I want to set the fill-color of a rectangle depending on a number stored in a counter. This is my try:

\documentclass{article}\usepackage{tikz}\usetikzlibrary{calc}\newcommand{\background}[1]{%\begin{tikzpicture}[overlay,remember picture]\fill [#1]        ($ (current page.north west) + (.7cm,-.7cm) $)        rectangle        ($ (current page.south east) + (-.7cm,.7cm) $);\end{tikzpicture}}\newcounter{test}\setcounter{test}{1}\newcommand{\chooseColor}{\ifnum\thetest=1 green \else red \fi}\begin{document}\background{green} % everything is good\newpage\background{\chooseColor} % throwing the error shown below\end{document}

Whilst \background{green} yields what I'm looking for, \background{\chooseColor} throws the following Error:

! Package pgfkeys Error: I do not know the key '/tikz/green ' and I am going to ignore it. Perhaps you misspelled it. 

I conclude from the error, that \background{\chooseColor} has been evaluated to 'green' correctly, however I get that error message. Is there anything I missed out on this one? I will be glad for every help!