Far away on a distant planet lived a culture of humanoids. The humanoids mostly came in two forms - those born with blue skin, and those born with pink skin. The skin colour of each newborn child was generally triggered by the genetic makeup of that child.
The humanoids needed to eat special fruits to keep their brains working well and to maintain skin pigmentation, and those fruits also came in both blue and pink forms.
The brains of the humanoids also mostly came in two forms - those which ran best on blue fruit and were happiest when their skin was blue ('blue brains'), and those which ran best on pink fruit and were happiest when their skin was pink ('pink brains').
And almost all of the time, blue-skinned people had a blue brain, and pink-skinned people had a pink brain. This observation became so ingrained into the culture of this planet that when every child was born, their skin pigment was immediately looked at, and the child was then only ever fed either blue or pink fruits, depending on which matched up with their skin pigment.
Because the vast majority of people were eating the right fruit, they never thought about what it might be like to eat the other type. And since the fruit was responsible for maintaining pigmentation, those who ate the other type of fruit would have their skin colour gradually shift towards the opposite one, and those who stopped eating fruit would have their skin turn grey; the majority of people didn't want that, since they were happy with the skin colour they had. So the other colour of fruit became off-limits, with many being taught that it was a societal taboo to eat the opposite-coloured fruit to the one you'd been told to eat, and a taboo to eat no fruit at all.
Over time, society developed and evolved. The rigid two-colour system where everyone was either completely blue or completely pink at birth became common knowledge, despite the fact it didn't always apply. Specific behaviours and stereotypes became expected from people depending on their skin colour. And for the most part, this worked well. But it didn't work for everyone.
A strange anomaly sometimes resulted in a child being born with purple skin. Most of those children had blue or pink brains, but it was hard to be sure what fruit to feed them because their skin colour wasn't blue or pink at birth, so often the parents or doctors simply guessed. Those children who were given the fruit which matched their brain would grow up in life happy. Those who were given the wrong fruit were less happy, and often suffered in varying amounts.
Another strange anomaly sometimes resulted in children with blue brains being born with pink skin, or children with pink brains being born with blue skin. This happened so rarely that because of the clearly visible skin colour, the parents or doctors just immediately assumed the brain matched up with the skin colour, and so the child was assigned a diet of fruits that didn't match up with their brain. Just like the purple-skinned humans given the wrong fruit, they would be less happy, and often suffered in varying amounts.
Rarely, the brain would expect a purple skin colour and needed a diet of both fruit mixed together to work best, with the specific fruit needed either varying or staying constant. It might also expect a grey skin colour, working best without any fruit. These cases were rare enough that society took a long time to acknowledge these types of brain could even exist, with many flat out refusing to accept it. And again, those with these brain types suffered, because they ate the wrong fruit.
For those eating the wrong fruit, sometimes they would eventually realise, which often manifested as the desire to eat the opposite colour of fruit, or the desire to stop eating the fruit they'd been told to, or as the feeling that their skin colour was somehow the wrong hue - almost like their brains were subconciously complaining about the mismatch. Many were not able to understand what these feelings meant, and only understood after hearing it described by others - but because this was considered a taboo subject, this would often not happen until many years into their life. It also took some many years to properly comprehend the feelings they experienced. Because these feelings were generally never experienced by those eating the correct fruit from birth, or they only appeared as fleeting curiosity and never persisted in those people, the persistent experience of those feelings became generally accepted as strong evidence of there being a mismatch.
For all those who realised, the underlying feeling that they had been eating the wrong fruit for their whole life would then never go away. The only established treatment known to get rid of this feeling was to switch them over to the correct diet of fruit. Over time, this would cause them to become happier, their brain function would improve, and their skin pigment would shift closer to the one that their brains expected, which gave relief from suffering. Unfortunately, the taboo on eating the opposite-coloured fruit created a major contention point, leading many who had spent their entire life eating the wrong fruit to be scared of switching over, and to be scared of expressing their feelings to friends and family for fear of rejection. Those who had purple or grey brains suffered even further, because many people refused to accept those brain types could even exist.
As people in society started to accept that a mismatch between someone's brain type and the fruit they'd been told to eat was possible, and that the only workable treatment in those cases was to correct their diet, the taboo began to be lifted, and this helped to ease the suffering of many. Some also accepted the existance of purple or grey brains, which began the process of helping those people too.
But some continued to cling onto the taboo regardless, because it was really difficult for them to accept something that had been a taboo for such a long time. Some who clung onto the taboo even went so far as to try to brainwash those suffering into thinking that they'd made a mistake, and that they didn't really need to change the fruit they were eating after all. Unfortunately, because the optimal fruit type was wired into each person's brain from birth, this simply didn't work, and sadly only served to cause suffering to continue.
Those experiencing a brain-fruit mismatch whose friends and family clung to these archaic taboos were faced with a problem. The only way they had to feel better was to change the fruit they ate; if they didn't, they'd be stuck suffering indefinitely. How do they help their friends and family not to feel uncomfortable?
The dilemma on this planet continues. Society can't really prevent the mismatches from occurring, and it probably wouldn't be ethical to do that anyway, so the only solution is to try and break the taboo. Sadly, every person who maintains the taboo continues to exacerbate the suffering of those who can't help but be themselves. Those with suffering friends or family can either persist with the taboo, which causes further suffering, or they can work hard to break their ingrained prejudices and be supportive, which can help the suffering to be alleviated. The latter can be a huge challenge, but is eventually the only long-term solution out of the deadlock.