I'm not going to lie, the Korean entertainment industry (and the popular culture in general) heavily focus on this certain ideal look that usually includes having pale skin. However Korea is starting to change and more and more black people are starting to get involved with their entertainment industries. Although not many, there are black girls (and guys) who are or have been doing well in the K-pop industry.
For instance, have you seen the girl who dances in Jay Park's music video "Know Your Name feat Dok2"? If not, go check that out (he also has an acoustic version but doesn't feature her). Then there's also Jay Park's friend and colleague Cha Cha Malone who is mainly a producer for AOMG (Jay Park's music label) but has also worked with other Korean artists. In addition, take a look at this page that I found listing other black artists in Korea: http://blackinkorea.com/pop-culture/four-black-k-pop-idols-you-should-know/
Korean musicians (mostly rappers and those) like Taeyang, G-Dragon, Rap Monster, Suga, and (I swear this is the last time I'll mention him) Jay Park have also been known to look up to black artists and their works. So it doesn't seem like they would discriminate against people just because of their skin color.
So yeah, there may not be a lot of black people in K-pop but things are getting there. The industry is still relatively new to non-Asians, so for now you won't find a lot of them yet but it doesn't mean that it's impossible for non-Asians to join. The thing that you should mostly be concerned about is to realize that it won't be a glamorous life all the time. Most K-pop idols start out as trainees where they train really hard for hours and hours every single day for many years before they even debut. They train for dancing, singing, and Korean (if you don't know Korean yet) until they become dancing and singing machines who are fluent in Korean. Then even after they debut, they still have to work really hard because debuting doesn't automatically mean success. K-pop idols have busy schedules where their dance moves are expected to be on point, they must always be in great shape, and they need to always look happy. Label companies are also notorious for controlling both the professional and personal lives of their stars as well as not giving them the wages that they deserve (compared to other kinds of celebrities). There have been times where label companies have been sued by their own stars for poor treatment and living conditions.
But if you're super passionate about K-pop and would still want to be an idol no matter what, then more power to you and good luck to you! Or as the Koreans say it, 행운을 빌어요!
