Update alert and add new example color

source/beamercolorthememetropolis-highcontrast.dtx

@@ -23,17 +23,18 @@
 %
 \usecolortheme{metropolis}
 
-\definecolor{mAlert}{HTML}{CA0047}
+\definecolor{mAlert}{HTML}{AD003D}
+\definecolor{mExample}{HTML}{005580}
 
 \setbeamercolor{normal text}{%
-  fg=black!98,
+  fg=black,
   bg=white
 }
 \setbeamercolor{alerted text}{%
   fg=mAlert,
 }
 \setbeamercolor{example text}{%
-  fg=black!50
+  fg=mExample,
 }
 %
 %    \begin{macrocode}