In Gbaya, the notion of something very white or bright is emphasized in the referenced verses with kpúŋ-kpúŋ, an ideophone that designates something that is very white.
Ideophones are a class of sound symbolic words expressing human sensation that are used as literary devices in many African languages. (Source: Philip Noss)
See also very white, teeth are like a flock of ewes, many-colored robes / white, and snow (color).