diff --git a/source/migrations/r4-r5.postgresql.sql b/source/migrations/r4-r5.postgresql.sql
new file mode 100644
index 0000000..b4c1949
--- /dev/null
+++ b/source/migrations/r4-r5.postgresql.sql
@@ -0,0 +1,34 @@
+-- calendars
+
+ALTER TABLE
+	"calendars"
+ADD COLUMN
+	"hue" INTEGER NULL
+;
+
+UPDATE
+	"calendars"
+SET
+	"hue" = (("id" * 40503) % 65535)
+;
+
+ALTER TABLE
+	"calendars"
+ALTER COLUMN
+	"hue" SET NOT NULL
+;
+
+COMMENT ON COLUMN
+	"calendars"."hue"
+IS
+	'scaled to a value between 0 and 65535'
+;
+
+
+-- _meta
+
+UPDATE
+    "_meta"
+SET
+    "revision" = 'r5'
+;