I prayed and after praying I noticed traces of menses blood in my clothes, is my prayer valid? May Allah bless you.
Yes, your prayers are valid. If a person prayed while there was a najasa on him and he did not know, his prayers are valid and he does not repeat them. Actually, if the person knew there was a najasa on his clothes and he intended to wash it but he totally forgot and he prayed, then after praying he remembered, his prayers are still valid. Don’t repeat it.
The condition of purifying yourself and your clothes from Najasa is different from the ruling of the condition of Wudu. Meaning, if a person prayed thinking he is in Wudu but after prayers he remembered that he did not make wudu, then he has to repeat the prayers.
I hope my answer was clear.