Hehe, I heard that. Reportedly, the law banning black cars was signed about 2 years ago (and the import of black cars was halted), but recently, it started acting. The traffic police evacuates all black cars and returns them after the owner pays a fine, and tell him* to repaint the car. They don't tell why, they only say "white color brings luck!". The repaint price has grown twice.
* - Why him? Because recently, in December 2017, women have been banned from driving cars. Although Saudi Arabia allowed its women to drive, there's now another country like this.
However, Turkmenistan (or Turkmenia, as we call it here in Russia) isn't completely like North Korea. They have access to Internet (but some sites like YouTube, Facebook and Twitter are blocked). They have presidental elections (after Niyazov's death). And it looks like they can leave their country. In my university, there was a guy from Ashkhabad studying with me. A funny guy, didn't look like he was oppressed or anything.