I read that it is haram but it is okay if you wanna lighten to go back to your original skin colour, since it doesn't alter creation of God. I used to be light when I was younger, but then I got tanned from hanging around the sun, and I want my original skin back because I like white skin, It's not like I'm gonna have plastic surgery. There are Halal whitening skin soaps as well.
The issue of altering or changing the creation of Allah has been clarified to us by Allah Himself. And Allah doesn't mention anything about actual person changing their body.
The real change in the creation is from Fitrah to associating partners with Allah or following a religion that is unacceptable.
Allah said in Surah ar-Rom 30:30 =
So direct your face toward the religion Hanifan, the fitrah of Allah upon which He has created people. No change should there be in the creation of Allah. That is the correct religion, but most of the people do not know.
And in a Sahih hadith, Rasolullah said =
"No child is born except on al-Fitrah and then his parents make him Jewish, Christian or Magian, as an animal produces a perfect young animal. Do you see any part of its body amputated?"
As you can see, "changing the creation of Allah" has absolutely nothing to do with what many have claimed it to be.
Lightening your skin doesn't fall under this category nor is there any ayah or sahih hadith forbidding anyone from doing that.
But keep in mind, if you doubt something is halal or haram, it's best to keep away until you're certain.