Reference: Fataawa Ramadhaan – Volume 2, Page 507, Fatwa No.465
Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-`Ilmiyyah wal-Iftaa. – Fatwa
Question: Is the fast of the woman who applies al-kohl (eyeliner) and dyes her hair during the day in Ramadhaan broken or not?
Response: Whoever applies eyeliner whilst fasting during the day in Ramadhaan does not break his [or her] fast, and likewise, whoever dyes his [or her] hair during the day in Ramadhaan whilst fasting does not break their fast.
And with Allaah lies all the success, and may Allaah send prayers and salutations upon our Prophet Muhammad (sal-Allaahu `alayhi wa sallam) and his family and his companions.