The orange color flame may be small particles of rust burning giving this color as would iron. The first thing would be to inspect the grill for being clean and the gas lines rust free.
It also depends on the system but the holes may be restricted cause more of less gas to release from areas with out an even burn. Again, this comes under cleaning the grill.
However, if your lines have become to rusty or just needing replacement, that would be the next step of action to take if cleaning does not help. Try cleaning before anything else and let us know how things are....We can also recommend reading what the manufacture may indicate about their equipment. Hope this helps and look forward to your course of action.