diff --git a/plantuml/sequence-diagram-tips.md b/plantuml/sequence-diagram-tips.md
index 69f7c37..7fe7c33 100644
--- a/plantuml/sequence-diagram-tips.md
+++ b/plantuml/sequence-diagram-tips.md
@@ -2,7 +2,9 @@
 
 You can change the colors of the arrows and messages as followings:
 
+```
 a -[#red]> b : <color blue> some message</color>
+```
 
 ## Collections