It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) said: "A woman whose husband has died should not apply henna, nor kohl, nor perfume, nor wear dyed clothing, nor wear jewellery."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20140