Black Color looks different

I had a BMW-2008 black color used car; since I got the car 1 year ago I noticed the hood under the sun (some spots) looks like dark brown. I has used many products such as Klasse (AIO and Maguire’s 205) by hand and still these spots are exist. I’m not sure what it is? Is that heavy oxidation or something else? I would appreciate your advice to get rid of these brown colors.
 
My first guess would be those areas have been repainted and the color wasn't properly matched. I've seen that on several black cars where under certain lighting conditions, some sections will look brown instead of black.
 
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