Is it obligatory to remove hair dye before wiping the head during Wudu'?

Hair matted with henna or similar substances does not affect ablution (wudu'), and it suffices to wipe over it. Sheikh Ibn 'Uthaymeen mentioned that a woman may wipe over her head if it is matted with henna or the like, arguing that the Prophet (peace and blessings be upon him) had matted hair during his ihram, which indicates leniency in purifying the head. 'Talbeed' (matting) is the application of a substance to the hair to make parts of it stick together.