Celie helps Shug by combing out her hair, which hasn't been combed for a very long time, and is considered quite messy, even by those like Mr. ____ who find Shug very attractive. As Celie works, Shug begins humming a tune that Celie enjoys, and thinks sounds "dirty." Shug answers that it's something she's just made up, something that Celie has "scratched out of her head."
Once again, Celie helps to comb out a woman's hair. This time, however, Shug is very desirous of exactly this, and she later considers Celie's kindness in this moment to be an important stepping-stone in their friendship and romantic relationship.