A mourning lady can wear clothes of ‘Asb.

Narrated Um 'Atiyya:

The Prophet ﷺ said, "It is not lawful for a lady who believes in Allah and the Last Day, to mourn for more than three days for a dead person, except for her husband, in which case she should neither put kohl in her eyes, nor perfume herself, nor wear dyed clothes, except a garment of 'Asb" Um 'Atiyya added: The Prophet ﷺ said, "She should not use perfume except when she becomes clean from her menses whereupon she can use Qust, and Azfar (two kinds of incense).

حَدَّثَنَا الْفَضْلُ بْنُ دُكَيْنٍ، حَدَّثَنَا عَبْدُ السَّلاَمِ بْنُ حَرْبٍ، عَنْ هِشَامٍ، عَنْ حَفْصَةَ، عَنْ أُمِّ عَطِيَّةَ، قَالَتْ قَالَ النَّبِيُّ ﷺ " لاَ يَحِلُّ لاِمْرَأَةٍ تُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ أَنْ تُحِدَّ فَوْقَ ثَلاَثٍ، إِلاَّ عَلَى زَوْجٍ، فَإِنَّهَا لاَ تَكْتَحِلُ وَلاَ تَلْبَسُ ثَوْبًا مَصْبُوغًا إِلاَّ ثَوْبَ عَصْبٍ ".