I think skin color preference has more to do with class distinction than with racial prejudice. Only in the 20th and 21st centuries has sun-tanned skin been admired. For centuries, a having tanned skin was a sign that you were an outdoor laborer, and therefore from a lower socioeconomic status. Think of the southern belles and their parasols.
I am not sure society does accept light skin tones over any other. I believe the argument comes down to racism and people who are racist are the ones who accept their own kind more than any other. Yes it has a historical relevance because during the times of slavery in America an African American would be looked upon as a slave and only a slave, they were judged purely on their skin tone.
For a period of time in history, many believed in the "Curse of Ham" from the story of Noah in Genesis, the Old Testament. I don't know much about this racist theory, but I have heard race ascribed to the story from Genesis 9: 20-27. I don't know if very many people continue to associate race with that story today, but the impact of people believing it in the past could probably continue to impact society.
Yes. In North America, slavery indeed led to racism. In the early 1600's in colonial Virginia, white, black and natives all could possess indentured servants or slaves. The predominant process was for the white indentured servant to gain freedom, and either solicit other indentured servants, or buy slaves, but it has been documented that blacks possessed other blacks and natives as slaves. by mid-century purchasing slaves became more economical than indentured servants; after Bacon's Rebellion in 1676, laws were instituted that effectively segregated the races -- blacks could no longer intermarry, own slaves, learn how to read, own any kind of property (real or personal) etc. The deliberate and legal segregation of the races led to institutional racism.
Look at the historical debate about whether or not slavery caused racism or racism caused slavery. Chicken and egg perhaps, but discrimination is not always socially based, and the economic and technological advantages of Europeans from the 1500's on helped to create a climate where racism against darker-skinned peoples was likely to occur.
Aggressive colonialism in the next four hundred years fueled racism, as it was used as a justification for conquering and subjugating peoples and nations.
There is no way to say for sure why society likes light skin better than dark skin, and it is not even completely true that (American society at least) does have this preference. We can only speculate about why.
The main reason why I think a light skin is more accepted now is because of the history of slavery and colonialism. Light-skinned people have tended to conquer, colonize, and/or enslave dark-skinned people. Because of this, a lighter skin tone has come to be identified more with the rulers and a darker skin tone with the conquered (who are therefore seen as inferior).
So, the main reason in my opinion is that people identify light skin with Europeans who were more advanced technologically and were therefore able to conquer other people. This makes light skin seem good. Dark skin is identified with the people who got conquered and so it seems bad.
I am not sure why people, in general, have greater preference for lighter colour in people rather than darker colour. However, it is quite unlikely that this has anything to do with slavery or colonialism. But it appears it has something to do with light generally being associated with something good and desirable while darkness being associated with something undesirable and evil. This dislike for darkness itself is perhaps because of our inability to see in the dark, which makes darkness something that is uncertain and therefore to be feared.
It might be a product of shelter and the types of structures that people built blocking out the sun and producing a certain type of skin tone. It could also be due to where one lived, and how strong they were. Light-skinned people were historically more advanced and could conquer darker-skinned peoples.
Discrimination is a psychological reason, caused by fear produced of a human group, from another different racial , ethnic or cultural group.