While shopping for paint for the baby's crib, Loren tells Dr. Quinn and Sully that blue is perfect for a baby crib and Sully replies, "What if the baby's a girl?" implying the blue/pink color split for babies what wan't in fashion until post World War I, and at that point the colors were flipped. Pink was more bold color for boys and blue was a delicate color for girls.
When Loren suggests painting the baby's cradle blue, Sully responds with "What if it's a girl?" Until the twentieth century the colors that we associate with gender were actually reversed; blue being for girls and pink was for boys. So Sully's response actually should have been "What if it's a boy?"