Again it's more about the socio economic strata than along racial lines. If you look at the history of racial strife, it's almost always been about economic competition, with the Draft Riots being a particularly dark stain.
As for the improved relations regarding the three groups I mentioned, do you think their ascension to acceptance was due to skin color or a complete assimilation into society across all economic strata? If skin color is the determinant, why aren't East Indians included?