Short answer
No. Dyeing hair is allowed, and for grey hair it is mustahabb (recommended) in the Hanafi school, ideally with henna or henna mixed with katam. Any colour is allowed except pure black, as long as the dye is pure and harmless and the look does not copy a sinful fashion. Wudu and ghusl are valid over normal hair dye.
Dyeing grey hair and the beard with henna or similar colours is mustahabb for men and women. Other colours are permitted in principle. Men may not apply henna to their hands and feet for adornment, as that is women's adornment, though it is allowed as medicine.
The four schools agree on this.
Explanation
The Prophet ﷺ told the Muslims that the Jews and Christians of his time did not dye their grey hair, and told them to be different. Several Companions, including Abu Bakr, dyed their beards with henna. So colouring grey hair is not just allowed: it is recommended. The four schools agree on this, and differ only about black dye, which is covered in is it haram to dye your hair black.
Which colours? Henna, henna with katam, red, auburn, brown and blonde shades are all fine. Bright fashion colours like blue, green or pink are not forbidden in themselves, but many Hanafi muftis discourage them for men when they copy a look tied to a sinful scene. A woman colouring her hair for her husband is doing something good.
Wudu and ghusl. Permanent and semi-permanent dyes soak into the hair and leave no layer, so water still reaches it and your purification is valid. The colour left by henna is also fine once the paste is washed off. Things that sit on top of the hair as a coat, such as hair paint, glitter sprays or thick wax, should be washed out before ghusl so water reaches every hair. See how to perform ghusl.
Ingredients. Avoid products that contain impure (najis) ingredients or that harm your scalp. If a dye causes an allergic reaction, stop using it.
The evidence
Quran, Surah Al-A'raaf 7:32
قُلْ مَنْ حَرَّمَ زِينَةَ ٱللَّهِ ٱلَّتِىٓ أَخْرَجَ لِعِبَادِهِۦ وَٱلطَّيِّبَٰتِ مِنَ ٱلرِّزْقِ ۚ قُلْ هِىَ لِلَّذِينَ ءَامَنُوا۟ فِى ٱلْحَيَوٰةِ ٱلدُّنْيَا خَالِصَةًۭ يَوْمَ ٱلْقِيَٰمَةِ ۗ كَذَٰلِكَ نُفَصِّلُ ٱلْءَايَٰتِ لِقَوْمٍۢ يَعْلَمُونَ ﴿٣٢﴾
Say, "Who has forbidden the adornment of Allah which He has produced for His servants and the good [lawful] things of provision?" Say, "They are for those who believe during the worldly life [but] exclusively for them on the Day of Resurrection." Thus do We detail the verses for a people who know.
Lawful adornment is allowed to believers.
Sahih al-Bukhari 3462
Sahih... إن اليهود والنصارى لا يصبغون فخالفوهم ...
"The Jews and the Christians do not dye their hair, so be different from them."
Encourages dyeing grey hair.
Sunan Abi Dawud 4205
Graded sahih... إن أحسن ما غير به هذا الشيب الحناء والكتم ...
"The best things with which to change grey hair are henna and katam."
Names the preferred dyes.
Where the ruling is recorded
- al-Fatawa al-Hindiyya, Kitab al-Karahiyya, chapter on adornment, rings and jewellery. Dyeing is mustahabb, and the ruling on henna for men.
- al-Durr al-Mukhtar with Radd al-Muhtar, Kitab al-Hazr wa al-Ibaha. Dyeing hair with henna is good.
- al-Majmu' (Nawawi), Kitab al-Taharah, chapter on the siwak and the practices of the fitrah. Nawawi on dyeing grey hair with yellow or red.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.