With contributions by MaddieFay. - Thanks!
This type of cuckold has a cuckoldress who only takes lovers from other races than that of the cuckold or the cuckoldress.
This is most often seen in white cuckoldresses or women with white cuckolds who only have sex with non-white men or women, but is occasionally seen using other combinations so long as either the cuckold or the cuckoldress is a different race from the chosen lover.
This is usually done either to make the cuckold feel belittled for a perceived inadequacy of his race or to add a feeling of exoticness to the cuckolding by providing a lover of a race that the woman may not ordinarily consider appropriate/acceptable given her background or upbringing.