Use colored blocks.

Define a custom inner theme to draw colored blocks with a top
border.

Makefile

@@ -1,6 +1,6 @@
 DESTDIR = dist
 
-STYFILES = beamerthemecpldn.sty beamerouterthemecpldn.sty beamercolorthemecpldn.sty
+STYFILES = beamerthemecpldn.sty beamerouterthemecpldn.sty beamerinnerthemecpldn.sty beamercolorthemecpldn.sty
 
 all: $(STYFILES) beamer-cpldn.pdf
 

beamer-cpldn.dtx

@@ -38,6 +38,7 @@ has been generated for details.
 \generate{
   \file{beamerthemecpldn.sty}{\from{beamer-cpldn.dtx}{theme}}
   \file{beamerouterthemecpldn.sty}{\from{beamer-cpldn.dtx}{outertheme}}
+  \file{beamerinnerthemecpldn.sty}{\from{beamer-cpldn.dtx}{innertheme}}
   \file{beamercolorthemecpldn.sty}{\from{beamer-cpldn.dtx}{colortheme}}
 }
 
@@ -130,12 +131,11 @@ has been generated for details.
 \mode<presentation>
 %    \end{macrocode}
 %
-% We specify the different themes to use. We use our own outer theme and
-% color theme, and the standard |rectangles| inner theme from the
-% Beamer distribution.
+% We specify the different themes to use. We use our own outer, inner,
+% and color themes.
 %    \begin{macrocode}
 \useoutertheme{cpldn}
-\useinnertheme{rectangles}
+\useinnertheme{cpldn}
 \usecolortheme{cpldn}
 \setbeamercovered{transparent}
 \setbeamertemplate{navigation symbols}{}
@@ -205,6 +205,50 @@ has been generated for details.
 % \fi
 %
 %
+% \subsection{The inner theme}
+% \iffalse
+%<*innertheme>
+% \fi
+%
+%    \begin{macrocode}
+\mode<presentation>
+%    \end{macrocode}
+%
+% Our inner theme is based on the standard |rectangles| theme from the
+% Beamer distribution.
+%    \begin{macrocode}
+\useinnertheme{rectangles}
+%    \end{macrocode}
+%
+% We redefine the |begin block| template to draw a border on the top of
+% the block.
+%    \begin{macrocode}
+\defbeamertemplate*{block begin}{cpldn}
+{
+  \par\vskip-1.4ex%
+  \begin{beamercolorbox}[colsep*=.75ex,ht=.2ex]{block top border}\end{beamercolorbox}
+  \ifx\insertblocktitle\@empty\else%
+  \nointerlineskip%
+  \begin{beamercolorbox}[colsep*=.75ex]{block title}
+    \usebeamerfont*{block title}\insertblocktitle%
+  \end{beamercolorbox}%
+  \fi%
+  {\parskip0pt\par}%
+  \nointerlineskip%
+  \usebeamerfont{block body}%
+  \begin{beamercolorbox}[colsep*=.75ex,vmode]{block body}%
+    \ifbeamercolorempty[bg]{block body}{\vskip-.25ex}{\vskip-.75ex}\vbox{}%
+}
+\defbeamertemplate*{block end}{cpldn}
+{\end{beamercolorbox}\vskip\smallskipamount}
+\mode<all>
+%    \end{macrocode}
+%
+% \iffalse
+%</innertheme>
+% \fi
+%
+%
 % \subsection{The color theme}
 % \iffalse
 %<*colortheme>
@@ -235,6 +279,9 @@ has been generated for details.
 \setbeamercolor*{title in head/foot}{fg=cpldndarkblue,bg=cpldnpalepink}
 \setbeamercolor*{date in head/foot}{fg=cpldndarkblue,bg=cpldnpalepink}
 \setbeamercolor*{frametitle}{fg=cpldndarkblue,bg=cpldnpink}
+\setbeamercolor*{block title}{fg=cpldndarkblue,bg=cpldnpink}
+\setbeamercolor*{block body}{fg=black,bg=cpldnpalepink}
+\setbeamercolor*{block top border}{bg=cpldnmagenta}
 \mode<all>
 %    \end{macrocode}
 %

sample.tex

@@ -50,6 +50,10 @@
     Phasellus eu tellus sit amet tortor gravida placerat.
   \end{block}
 
+  \begin{block}{}
+    A title-less block.
+  \end{block}
+
 \end{frame}
 
 \section{The Second Section}