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+## Arrow colors
+
+You can change the colors of the arrows and messages as followings:
+
+a -[#red]> b : <color blue> some message</color>
+
+## Collections
+
+There is a "collections" participant type:
+
+```
+collections "Things" as things
+```
+
+## Hidden returns
+
+There is sometimes some weirdness when returning after a self call when there is no explicit return.  You can add a hidden return to fix this using:
+
+```
+a -> b++ : do stuff
+b -> b : do stuff to self
+b -[hidden]-> a : hidden return to fix weirdness
+```