diff --git a/preamble.tex b/preamble.tex
index 8f1ecea..c428907 100644
--- a/preamble.tex
+++ b/preamble.tex
@@ -1,3 +1,6 @@
 %! TEX root = ./thesis.tex
 
 \input{tikz/tikzpreamble.tex}
+
+\definecolor{myteal}{HTML}{228c9c}
+\DeclareTColorBox{blockbox}{ O{width=\textwidth} }{boxrule=0mm, colframe=myteal, valign lower=bottom, on line, lower separated=false, height=.6\textheight, #1}