Sunan an Nasai
3536
Sahih+2

It was narrated from Umm 'Atiyyah that the Prophet said:"It is not permissible for a woman who believes in Allah and the Last Day, to mourn for anyone who dies for more than three days, except for a husband; she should not use kohl, dye nor wear dyed clothes

SahihAbu Ghuddah
SahihAl-Albani