I would like to just offer a thought form someone old enough to have played innocently with a golliwog / collected gollys from jam jars as a very young child and who then saw the minstrels on tv and did not actually know the singers were not black. I had never seen anyone in person not caucasion then ( don't worry, it did not scar me ... I grew up to regard all people no matter skintone as just people as long as they were nice lol and thought my mums suggestion I marry a bf from WI to annoy the racist neighbours almost as racist !)
Would it be disingenious / insulting to ignore skin tone when dressing in the manner of another culture ( caveat that its not a drunken party with people mocking other cultures !) if celebrating a culture not ones own. Could it be viewed that I for example was viewing my “superior” pink skin as not needing altered and was better than say a darker skinned person who wears traditionally a sari or African tribal dress.
Subtly altering ones skin tone is very different from blacking up aka the boot polish black with white lips / eyes as a parody ( no one has said how the cousin has altered skin tone) ….. or making fun of stereotypes at a drunken party. I am Scottish and the stereotype of my heritage is a drunken, whiskey swilling, string vested, kilted man with wild orange hairy body yelling “Och aye the noo” or singing Flower of Scotland. Some scots may indeed have some of those traits, its how stereotypes come into being……. but its racist to poke fun at or believe that all scots look like and behave like this. I would not put boot polish on my face to parody a Jamaican as the cousin in the post but one cannot escape the popular image of Jamaican musicians as having rasta hair and wearing those colourful hats and having great fun at parties ( probably not everyday life in Jamaica but relevant to a party night? ) and honouring a skin tone might be the intent.
As to the arising points about racism / repression / slavery and how this affects people with dark skins far more that those with white skin. I think that many are restricting their historical reference to the modern age and choosing to reference African American people as the main victims of this. Slavery, repression and predjudice according to colour is not and never has been one way. Statistics and historical references are available that show that African, Arabian and other darker skinned nations pillaged the European continent and even went as far north as Iceland to collect white slaves. White settlers entering Africa usually only had to go to the markets to get slaves, the peoples of Africa often enslaved / repressed other tribes so it was not just a colour thing. It was not just the white Americans that had slaves, mexicans did too. Irish and chinese people were also taken to America and were enslaved so its not just a colour thing.
People of all races have in history have repressed others and still do experience it, black people do not have the monopoly on it ….. just the loudest voice to proclaim actual, as well as perceived, racism or inequality because of modern media. This brings it much more to the forefront than any other race in history. That is not to say its acceptable or that is does not happen …… but to say that just because only certain can define what is racist or not and STATE IT AS FACT at a such a personal level is kinda taking us towards a state of Big Brother which makes for just as terrible a situation.