Thank you man!
You just need to dash yourself and all will be good! The longest and laborious part is to well protect the entire car to avoid bad surprises. I used the tamiya scotch witch is really easy to use and the Rewell stop color for more delicate parts that are hardly reachable with the scotch.
After i understand that it is delicate to modify a 700$ collectible but honestly no regret!
Personaly the right color in the mood of the movie is a dark bronze/gunmetal.
I tried to get closer of this:
As said previously, in Batman returns the rims are full black so they appear black but in 89 the rims are more dark gunmetal but appear dark, quite black in the entire film due to the fact that we often see the car at nightime.
On the photosets or promotional photos, they appear light gunmetal or silver due to the lights of the set or flash but for me the batmobile is more accurate, in the mood and beautiful with dark rims .
To answer to Roberto yes Hot Toys get wrong with the stock rims which are really too light but it's my personal opinion and maybe some of us are happy with the stock color and it's good.
I think I'm gonna leave mine as they are for the time being. I'm sure I've got plenty of other statues, etc that are not 100% movie accurate which don't bother me too much so I guess this will be another one 
