The coat of arms of Natal has a immediately noticed meaning, and I think it's good: "Natal", in Portuguese, means "Christmas", a reference to the date of city's foundation, so it depicts the Star of Bethelem. There are some errors, accordingly to Brazilian heraldic rules, and, guaranteeing it's not a replication error, the image was took from city's governmental website, although it's seen, in the same way, in many other sources. Here's a list of rule breaks I noticed:
- The mural crown shows nine visible towers, while, by a standard inherited from Portuguese settlers, a city should use a mural crown with five visible towers.
- Being Natal the capital city of Rio Grande do Norte, this mural crown should be golden, in recognition of this special status.
- The coat of arms is placed in a English shield shape, while a Spanish escutcheon should be rather used.
- This next isn't exactly a broken rule, but would make it more good-looking: change the direction of the motto's strip.
Specifically in the flag, I would suggest the change of green tone to the same used in Rio Grande do Norte state flag. Applying this suggestions, I created two proposals: one without the motto, what's vexillologically recommended, and one with it, as commonly the coat of arms are depicted in Brazilian flags.
And a bonus flag: why not a banner of arms?
Finally, I'd like to note that, while some cities and states follow rigorously the Brazilian heraldic rules, most probably the bigger part of them doesn't.
If you want to give any kind of comment, feel free to do it. I'd be pleased.
I'll try again later send the letter to the prefecture. If I obtain success, I'll inform it on the blog.