Undefined color when using tikz inside beamer class

Question

I am in the beamer class, and using tikz. I want to use a color from the xcolor package, but am not able to get it working. Here is my preamble.

\documentclass[usenames, dvipsnames]{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{libertine}
%\usepackage[font={small}, labelfont=bf]{caption}
%\usepackage{subcaption}


\usetheme{Cuerna}

%\usepackage{amsmath,commath,amssymb,amsthm,blkarray}
%\usepackage{bbm}
%\usepackage{mathtools}
%\usepackage{booktabs}
%\usepackage{array}


%\usepackage{siunitx}
%\newcommand{\imp}[1]{\textbf{#1}}
%\renewcommand{\vv}[1]{\mathbf{#1}}
%\DeclareMathOperator{\inff}{inf \;}
%\DeclareMathOperator{\supp}{sup \;}
\usepackage{tikz}
\usepackage{pgfplots}
%\usepackage{physics}
\addtobeamertemplate{navigation symbols}{}{%
\usebeamerfont{footline}%
\usebeamercolor[fg]{footline}%
\hspace{1em}%
\insertframenumber/\inserttotalframenumber
}

\setbeamercolor{itemize item}{fg=midnightblue}
\setbeamertemplate{itemize items}{\begin{tikzpicture}
\shade[ball color=midnightblue!50!white, preaction={fill=black,
opacity=.25,transform canvas={xshift=1mm,yshift=-1mm, yscale=0.5}}] (0,0)      circle (0.6ex);
\end{tikzpicture}}
\title{Project}
\author{Name}
\begin{document}

\begin{frame}
 \titlepage
\end{frame}

\section{Introduction}
\begin{frame}
\begin{itemize}
    \item something random
\end{itemize}
\end{frame}
\end{document}

I have seen similar questions, but none of the suggestions have worked, such as loading in the package xcolor explicitly, or changing the order of when it is loaded.

Answer 1

• if you want to pass options to the xcolor package, use xcolor={usenames, dvipsnames}

• the name of the colour is MidnightBlue not midnightblue

• there is a missing } at the end of \addtobeamertemplate{navigation symbols}{}{}% (in its current form this command does nothing...)

• \renewcommand{\vv}[1]{\mathbf{#1}} won't work because vv is not defined previously

---

\documentclass[xcolor={usenames, dvipsnames}]{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{libertine}
\usepackage[font={small}, labelfont=bf]{caption}
\usepackage{subcaption}


\usetheme{Cuerna}

\usepackage{amsmath,commath,amssymb,amsthm,blkarray}
\usepackage{bbm}
\usepackage{mathtools}
\usepackage{booktabs}
\usepackage{array}


\usepackage{siunitx}
\newcommand{\imp}[1]{\textbf{#1}}
\newcommand{\vv}[1]{\mathbf{#1}}
\DeclareMathOperator{\inff}{inf \;}
\DeclareMathOperator{\supp}{sup \;}
\usepackage{tikz}
\usepackage{pgfplots}
\usepackage{physics}
\addtobeamertemplate{navigation symbols}{}{}%

\setbeamercolor{itemize item}{fg=MidnightBlue}
\setbeamertemplate{itemize items}{\begin{tikzpicture}
\shade[ball color=MidnightBlue!50!white, preaction={fill=black,
opacity=.25,transform canvas={xshift=1mm,yshift=-1mm, yscale=0.5}}] (0,0)      circle (0.6ex);
\end{tikzpicture}
}

\begin{document}

\begin{frame}
content...

\begin{itemize}
\item test
\end{itemize}
\end{frame}


\end{document}