All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, we would like to congratulate you for reverting to Islam, and you have done well by wearing the hijaab. We ask Allah to bless you with happiness in this life and in the afterlife and to grant us all steadfastness on the Straight Path until the Day that we meet Him.
In principle, it is the duty of the Muslim woman to obey her husband in whatever is lawful and good. Some scholars specified that the enjoined obedience to the husband is in the matters relating to their marriage, which includes what the wife does to beautify herself for her husband. Therefore, she is obliged to obey her husband in this regard. The husband often loves to see his wife in her best looks. Abu Umaamah, may Allah be pleased with him, narrated that the Prophet, sallallahu ‘alayhi wa sallam, used to say, "Nothing is of more benefit to the believer after Taqwa (piety) than a righteous wife whom, if he commands her, she obeys him; if he looks at her, she pleases him; if he swears an oath concerning her, she fulfills it; and when he is away from her, she protects his honor and his wealth." [Ibn Maajah]
People view such matters (like hair coloring) differently, so it is better for the wife to do what her husband likes to win his affection and strengthen their marriage bonds. If the wife wishes to do her hair in a certain way or color it, she should try to reach a mutual understanding with her husband, and the husband should not insist on preventing her from doing what she likes as she might have another acceptable motive, such as beautifying herself before her fellow Muslim sisters. Lastly, please note that dying the hair black is forbidden according to a prophetic hadeeth, so this must be avoided in all cases. For more benefit, please refer to fatwa 83976 and 92366.
Allah knows best.