Jews aren't all white, and Palestinians aren't all brown, but that doesn't matter because society only focuses on dichotomies.
the Western world sees Jews as white and Palestinians as brown, then treats them according to those racial codes. This means that even if both groups are ethnically diverse, the West prioritising Jewish lives over Palestinian lives is a reflection of the West's prioritisation of white people over brown people.
So yes Israel is upholding white supremacy, and that's not even going into the details of
- racism between different Jewish ethnicities (i.e. Ethiopian Jews being sterilised, Arab Jews having to deal with social slums, not considering multiple Jewish ethnic groups from India as Jewish, the face of Jewish people only being white-passing Ashkenazi Jews, etc)
- the dehumanising racist language used by Israeli media and officials ("children of light vs dark" "they are like animals. They aren't human" etc)
- the very fact that Israel was founded as a colony (Jewish people are descended from those from the Levant, but so are Palestinians. The modern state of Israel was not founded as landback but rather as a tool for colonisation, which is why so many of the tactics used by Israel involve displacing Palestinians, forming a racial hierarchy between Jewish ethnicities, and changing the ecosystem to mimic Europe)