Job's profound physical and emotional agony is laid bare through the striking image of his outward appearance and his desperate public cries. His physical form has become darkened and blackened [מצודת ציון, מלבי״ם]. The primary approach among commentators is that this blackened skin is not a natural result of the sun's rays. Instead, his dark appearance stems entirely from the sheer weight of his troubles and suffering.
This unnatural darkening carries a deeper meaning regarding his condition. A normal sunburn naturally fades when a person steps into the shade. However, because Job's dark state is not caused by the sun, he understands that it will not simply pass. He feels his suffering came upon him without any sin, leaving him with no hope that his pain will naturally wash away on its own [מצודת דוד]. Another perspective suggests that this darkness is internal, as Job walks in such deep emotional shadows that he is completely unable to feel the warmth or light of the sun [ביאור שטיינזלץ].
Driven by despair and the realization that his suffering will not leave on its own, Job takes action by standing in the middle of a large crowd to cry out [מצודת דוד]. His immense pain simply does not allow him to remain silent. The agony is so overwhelming that he is forced to scream, not just in the privacy of his own home, but even when surrounded by people [ביאור שטיינזלץ].
Alternatively, this public outcry is seen as an active attempt to stir the mercy of the community. Job's shocking appearance, blackened without the sun, should have been enough to awaken the pity of anyone who saw him. When he realizes that his silent suffering is not enough to move the onlookers, he stands and cries out to God right in the middle of the assembly. His hope is that the people around him will finally be moved to join his prayer and beg God for mercy on his behalf [אלשיך].