Putting aside the fact that all parties
do get the joke and find it humorous, the joke itself implies a racist attitude of positioning white skin as the baseline, and dark skin as consequently abnormal (or even “dirty”). However, when Tagaran understands the joke and runs with it, it shows that both she and Rooke are becoming very proficient in the unspoken aspects of language that allow them to successfully make jokes. Their friendship is also strong enough by this point to make such jokes acceptable.