Update src/hb-ot-color.cc

Co-Authored-By: Khaled Hosny <khaledhosny@eglug.org>
diff --git a/src/hb-ot-color.cc b/src/hb-ot-color.cc
index bde36ca..f3afe0c 100644
--- a/src/hb-ot-color.cc
+++ b/src/hb-ot-color.cc
@@ -192,7 +192,7 @@
  * hb_ot_color_has_layers:
  * @face: #hb_face_t to work upon
  *
- * Tests whether a face includes any COLR color layers.
+ * Tests whether a face includes any `COLR` color layers.
  *
  * Return value: true if data found, false otherwise
  *