Is it permissible to adopt the fatwa that describes yellowness (صفرة) as clear colors like egg yolk, and disregard the other fatwa that describes it as "yellowness of straw or tooth," in order to avoid hardship and obsessive doubts?

Leave these whispers (waswas) aside. If you doubt whether the discharge is yellowish (ṣufrah) or from vaginal secretions, the default is that it is not yellowish, and the default is that these secretions are pure and are from the natural vaginal moisture.