# Changing color of already printed text

For making a small quiz in class I am working on a presentation in beamer.

I want to change the color of statements to red (wrong statement) or green (right statement) but only after my class answered the question.

I was searching the internet, but only found the color package, where you apparently can only change the text color before it appears.

Can someone point me into the right direction?

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beamer provides an overlay specification with most of its macros/environments. It allows you to say (for example) ...\alert<2>{<stuff>}... so that <stuff> prints normally on slides other than number 2. \color itself is overlay aware in the form \color<2->{blue}{<stuff>} that would print <stuff> in blue from slide 2 onward. Alternatively, one can use something like ...{\only<2>{\color{blue}}<stuff>}... which prints <stuff> in blue only on slide 2.

Here's a short example

\documentclass{beamer}% http://ctan.org/pkg/beamer
\begin{document}
\begin{frame}
Some text {\only<2>{\color{blue}}and stuff}.
\end{frame}
\end{document}


Note that beamer already loads xcolor.

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This is exactly what I need, with one little modification: I want the blue stuff be shown after, say, slide 2. –  mcwise Nov 1 '12 at 21:34
I found it on the documentation page you linked, I will have to write \only<2-> and so on. Thanks! :) –  mcwise Nov 1 '12 at 21:36