Praise be to Allah.
It was narrated from the Prophet (peace and blessings of Allaah be upon him) that dying the hair black is not allowed. That is mentioned in the hadeeth of Jaabir ibn ‘Abd-Allaah (may Allaah be pleased with him) that Abu Quhaafah, the father of Abu Bakr al-Siddeeq, was brought to the Prophet (peace and blessings of Allaah be upon him) to give his oath of allegiance, and his hair was completely white. The Prophet (peace and blessings of Allaah be upon him) said: “Change this, but avoid black.” Narrated by Muslim.
Dyeing the hair black is not allowed, whether the hair was red or white. The scholars have stated that the reason why it is not allowed to dye the hair black is because of the deception involved, as it makes a person appear to be something he is not, especially since a person’s age may be known from the colour of his hair, whether it is black or white or a mixture of the two. So dyeing the hair black makes him look young when he may be middle aged or an old man.
Based on this reason, if there are no white hairs and there is no intention to deceive, as in the case asked about here – where the questioner’s hair was black then its colour changed to red – is it permissible to dye the hair black?
It better to be on the safe side and avoid that, because of the wording of the hadeeth and in accordance with it, especially since the reason mentioned – namely cheating and deception – is an implicit reason which some of the scholars stated was what was meant here, but it was not stated expressly by the Prophet (peace and blessings of Allaah be upon him).
It should be noted that the Muslim woman understands the importance of time, and recognizes that this world is a preparation for the Hereafter. So she should not spend much of her time or most of her time on matters of her body, clothing and adornments at the expense of her worship, educating her children, calling others to her religion and treating others with kindness. That does not mean that she should not adorn herself, rather she should adorn herself with that which Allaah has permitted, within reasonable limits as regards how she does it and how much time she spends on that.
Moreover she should not pay attention to every new thing that comes along, adopting and following every new fashion that she sees. That may lead her to imitate kaafir women and immoral women, let alone wasting time and money that she could put to better use which would be more beneficial to herself and to her ummah.
And Allaah is the One Whom we ask to guide us to do and say that which is right and true.