I have a couple of questions.
1) Is it true that LEDs' Blue's make the color pop better?
Pop is a highly technical term and hard to understand! 
Blue light is the high energy end of the visible spectrum. Many of our corals (not all by any means) have pigments (like you or me turning brown or red when we go in the sun) that take in the high energy blue light, use some of that energy and then 'fluoresce' their own light. That is probably what you are describing as 'pop'?
2) DO al LED's produce the same blue color that make your corals brighter?
Not all, but most aquarium led fixtures sold these days do to some extent. And some do it better than others. When leds were first tried over aquariums they didn't have any blue at all. They were all white. And there are different spectrum of blue light. 400nm wavelength is the cutoff between UV (less than 400nm) and violet (more than 400nm). Violet then becomes blue and there are leds available at several wavelengths that are blue, 420nm and 440nm are considered violet, 460nm, 480nm and 490nm are all blue. Above 500nm wavelengths are getting into green.
3) will the Cheaper CHINESE LED BLACK BOX lighting work?
In a word, yes! I think there is a company called Chinese Blackbox who sells led fixtures and then there is the common term Chinese black box which refers to a large assortment of companies selling led fixtures made in China. Most of these are enough to grow almost any coral given all the other parameters in your system are also equal to the job. I have used a variety of cheap and inexpensice Chinese led fixtures over the last 4 years. Some are cheap and can have 'issues'. Others are still inexpensive as far as led fixtures go, but are good enough to be considered above average quality (IMHO).
4) Will the CHIENSE LED BLACK BOX be enough to grow mixed corals? zoas, SPS, LPS, etc.
I have 4 tanks, all with led fixtures and for the last 3 years I've grown all kinds of coral. See photo below of my main tank. I even have some I have collected personally when snorkeling in the Florida Keys (I have the proper license so it's legal).
5) Someone locally is selling it for $50, was wondering if it's worth the pick up?
It's hard to say if anything being bought used is "worth the pick up." Is the $50 a big deal to your budget? Do you trust the seller? If it dies in a month, will replacing it be a financial burden? If so, maybe buying a new MarsAqua for $85 with a warranty would be a better decision? If the $50 is no big deal, sure, a good led fixture for $50 is a nice deal. Do you know the brand and model number? Do you know how old it is?
I hope that helps some? If you have more questions just ask.
