Fix type of color field of codelet

doc/doxygen/chapters/api/codelet_and_tasks.doxy

@@ -415,7 +415,7 @@ compiler implicitly do it in e.g. static storage case.
     Optional name of the codelet. This can be useful for debugging
     purposes.
 
-\var const char *starpu_codelet::color
+\var unsigned starpu_codelet::color
     Optional color of the codelet. This can be useful for debugging
     purposes.