Question. After brushing my teeth, I often find blood in my saliva. Would this invalidate my wudu?

Answer: If the blood predominates or is equal to your saliva; your Wudu will be nullified. This is usually when the saliva is red in colour. However, if the saliva is whitish, yellowish or just slightly red, the Wudhu will not be broken.

وينقصه دم غلب على بزاق حكما للغالب او ساواه ولا ينقضه المغلوب بالبزاق (الشامي ج1ص139)

And Allah Knows Best

Yusuf Moosagie