Colored underline, with Beamer overlay support

cul.sty

% colored underline, with Beamer overlay support                                                                                                                                                                                                                                                                                                                                                                                         
% usage: \cul{x} or \cul[blue]{x} or \cul<2->{x} or \cul<2->[blue]{x}                                                                                                                                                                                                                                                                                                                                                                    
\newcommand<>{\cul}[2][red]{%                                                                                                                                                                                                                                                                                                                                                                                                            
  % change underline dimentions: https://tex.stackexchange.com/a/167957/25264                                                                                                                                                                                                                                                                                                                                                            
  \fontdimen8\textfont3=0.75pt%                                                                                                                                                                                                                                                                                                                                                                                                          
  % colored underline: https://tex.stackexchange.com/a/9477/25264                                                                                                                                                                                                                                                                                                                                                                        
  % transparent underline: https://tex.stackexchange.com/a/45601/25264                                                                                                                                                                                                                                                                                                                                                                   
  % switch between colored and transparent: http://mirrors.ibiblio.org/CTAN/macros/latex/contrib/beamer/doc/beameruserguide.pdf sections 9.3 and 9.6.1                                                                                                                                                                                                                                                                                   
  \alt#3%                                                                                                                                                                                                                                                                                                                                                                                                                                
      {\color{#1}\underline{{\color{black}#2}}\color{black}}%                                                                                                                                                                                                                                                                                                                                                                            
      {\transparent{0.0}\underline{{\transparent{1.0}#2}}\transparent{1.0}}%                                                                                                                                                                                                                                                                                                                                                             
}