+/** Calculate color traces over the specified set of representation labels.
+ *
+ * @param e Expression to take the trace of
+ * @param rls Set of representation labels */
+ex color_trace(const ex & e, const std::set<unsigned char> & rls);
+
+/** Calculate color traces over the specified list of representation labels.
+ *
+ * @param e Expression to take the trace of
+ * @param rll List of representation labels */
+ex color_trace(const ex & e, const lst & rll);
+
+/** Calculate the trace of an expression containing color objects with a
+ * specified representation label.
+ *
+ * @param e Expression to take the trace of
+ * @param rl Representation label */
+ex color_trace(const ex & e, unsigned char rl = 0);