TBH, I feel like in most healthy societies and in most healthy males and females, there is a strong preference for a significant other that looks like them. Just my own observation but I notice that whenever women don't like or go for men that look similar to them, there is usually some red flag in them that becomes evident. In men, I notice the same thing. Guys that do not go for women of their own background or women similar to them have some degree of confidence, security and other kinds of issues and are usually more insecure than usual.
For example, I notice that natural blondes that are hot and genetically gifted tend to like blond guys. Will they go for a darker guy, minority or a white guy with dark hair? They will, but usually he is hitting it out of the ballpark in so many ways that they go for him in spite of him not looking like what they are used to, not because of it.
Every woman I have known that hated men of her nationality and race/ethnicity was screwed up in the head. Good example are the Asian girls that bleach their hair blonde and talk about how awful Asian men are. The white guys who marry these "feminine" Geishas always end up in a miserable relationship.
Similarly with guys, I notice that swarthy dudes who obsess over blonde girls usually have massive inferiority complexes about their own appearance and are trying to use women to fill those complexes. Healthy and quality women pick up on this and immediately reject these guys. They do get their dream blonde after a lot of trying but she is riddled with more than enough insecurities, issues, and other problems of her own that these guys aren't exactly striking gold.
A common trait I have seen in mentally healthy and successful men and women is that very desire to go for others who look somewhat similar to them even if they are not of the same nationality.
One of my Arab friends (Algerian) is brown and he loves Latinas, Indian women, Persian women, and Arab women the most. The guy has also dated the hot blondes other Arab dudes would give an arm and a leg for.
Meanwhile, I had a former Persian coworker who was trying to force everyone to believe that Persians are as white as the Scandinavians and was obsessed with blonde women. Needless to say he was borderline incel despite not being an ugly dude and struggled with women a lot because he was insecure in his own skin.
Whenever people obsess over a look different than their own and disregard those who look similar to them, there is almost always an insecurity as well as other major issues out there.