As with colour, you could, in theory, create razor sharp definitions: wavelengths of about 680 to 740 are defined as red.

With a database of your genetic stock, you could simply say: these clusters define the White race. You could also sperg out, go further and support certain genotypes over others or reintroduce certain alleles or whatever. That is all possible, on paper. Is it necessary, though? A fast, soft definition would be someone who has at least three White grandparents.

Above all else, rekindling healthy racial consciousness is the first and most important step.