All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
It is confirmed that the Prophet said, “The first group of people who will enter Paradise will be glittering like the full moon, and those who will follow them will glitter like the brightest star in the sky...” [Al-Bukhari and Muslim]
Also, the Prophet said about the Muslims who would come out of Hellfire and be admitted to Paradise, “They will enter one of the rivers of Paradise and bathe in it, and when they come out, they will be as white as paper…” [Muslim]
The scholars said, “He [Prophet] said that they were like paper because of them being so white after bathing and because the blackness that was on them was removed.”
As regards what was reported about the people of Hellfire, that they will be given white skin, this was narrated by Ibn Jareer and Ibn Abi Haatim from the reports by Ibn ‘Abbaas and Ibn ‘Umar about the interpretation of the verse in which Allaah says (what means): {Every time their skins are roasted through We will replace them with other skins so they may taste the punishment...} [Quran 4:56]; Ibn ‘Abbaas said, “When their skins are burned, they will be given another skin in replacement, and this skin will be as white as paper.”
The chain of narrators of the reports of Ibn ‘Abbaas and Ibn ‘Umar includes a weak narrator, Thuwayr ibn Abi Faakhitah. Ad-Daaraqutni said that this narrator is abandoned (i.e. rejected), and Sufyaan ath-Thawri said about him, “Thuwayr was one of the pillars of lying (i.e. he was a great liar).”
Even if we presume that it is correct that the skins of the people of Hellfire will be changed to white color, then this is not for them to enjoy like the people of Paradise but to be tortured again when their skins are roasted. So there is no reason for being surprised or confused.
Allaah knows best.