diff --git a/plantuml/lecture-colours.ipu b/plantuml/lecture-colours.ipu
index 0914c68..098c168 100644
--- a/plantuml/lecture-colours.ipu
+++ b/plantuml/lecture-colours.ipu
@@ -42,8 +42,8 @@
 		MessageAlign center
 
 		Participant {
-			BackgroundColor #F2F2F2
-			BorderColor #3f3f3f
+			BackgroundColor #f2f2f2
+			BorderColor #7f7f7f
 			FontColor #3f3f3f
 			FontSize 16
 		}
@@ -73,7 +73,7 @@
 
 		Box {
 			BackgroundColor #F2F2F2
-			BorderColor #3f3f3f
+			BorderColor #7f7f7f
 			FontColor #3f3f3f
 		}
 	}