Simple box in beamer

Question

I'm looking for a beamer theme with a simple box around each frame. Just a coloured rectangle, really. I tried to frame each slide myself with tcolorbox, but I can only make it start below the frame title. How would I go about making a box like the one in the picture below? Or is there a preset theme that I haven't found yet?

Answer 1

Following code could be a solution. It draws a rectangular TikZ node in background. You have to compile twice to see the rectangular border.

\documentclass{beamer}
\usepackage{tikz}
\setbeamertemplate{background canvas}{%
    \begin{tikzpicture}[remember picture, overlay]%
    \node[draw=blue, thick, minimum width=.975\paperwidth, minimum height=.95\paperheight] at (current page.center){};
    \end{tikzpicture}}
\begin{document}
\begin{frame}{Testing Background Image}
    Hello!
\end{frame}
\end{document}