\documentclass{report}
\usepackage[table]{xcolor}
\definecolor{lightblue}{rgb}{0.93,0.95,1.0}

\begin{document}
 \rowcolors{1}{lightgray}{white}   %% <--- here
 \noindent
 \begin{tabular}[!ht]{>{\bfseries}l <{\raggedright}p{10cm}}
      \rowcolor{black!90}\textcolor{white}{Identifier/Name} & \textcolor{white}{\textbf{UC1 - Login}}  \\
      Importance    & 5/5\\
      Difficulty    & 1/5\\
      Actor(s)      & Generalized User\\
      Goal          & To allow the user to access the system.\\
      Preconditions & The user is at the login page. \\
      Summary       & Will validate the users name and password and subsequently give them access to the
      system.\\
      Steps         & 
                      {\begin{tabular}{@{}p{4cm} | p{4cm}@{}}
                          1. User provides username and password. & 2. System directs user to main system page. \\
                      \end{tabular}} \\
      Postcondition & \textbf{Success:} User is logged in. \newline \textbf{Failure:} The system reamins at the login state. \\
  \end{tabular}
\end{document}