Praise be to Allah.
It is recommended to change grey and white hairs with something other than black, because of the hadith of Abu Hurayrah (may Allah be pleased with him), who said: The Prophet (blessings and peace of Allah be upon him) said: “The Jews and Christians do not dye their hair, so be different from them.” Narrated by al-Bukhari (5899).
It was narrated that Jaabir (may Allah be pleased with him) said: Abu Quhafah was brought on the day of the Conquest of Makkah, and his hair and beard were white like hyssop. The Messenger of Allah (blessings and peace of Allah be upon him) said: “Change this with something, but avoid black.” Narrated by Muslim (2102).
It is not permissible to cheat and deceive when proposing marriage, which includes dying grey or white hairs with black, or something close to it, so as to conceal the matter and make people think that there are no grey or white hairs, because the Prophet (blessings and peace of Allah be upon him) said: “Whoever deceives (people) does not belong to me.” Narrated by Muslim (102).
An-Nafrawi al-Maliki (may Allah have mercy on him) said:
It is disliked to dye with black hair that is not black, for any purpose that is not prescribed according to Islamic teachings…
But if that is done for the purpose of deceit, such as when wanting to marry a woman, there is no doubt that it is prohibited…
Then he explained what is meant by black being allowed by saying: There is nothing wrong with dying the hair with henna for the length of time that is required to redden the hair, and with katam, which is the leaves of the sullam plant, which turn the hair yellow…
Rather it is disliked to dye the hair with black, unlike other colours, because it is changing it from one colour to another, with the loss of the first colour, in contrast to dyes like henna, because the first colour does not disappear completely; rather it is changed, so no one will be deceived about grey hair if someone has dyed it red or yellow."(Al-Fawakih ad-Dawani 2/307-308).
It says in Matalib Uli’n-Nuha (1/89): It is disliked to change grey or white hairs with black in situations other than war, and it is prohibited if that is done for the purpose of deceit. End quote.
So you may refrain from dyeing the hair, or tell them about it, or dye it with red or yellow in such a way that no one who sees you will be deceived.
And Allah knows best.