It is normal for women to experience vaginal discharge at different times of their cycle. Depending on a woman’s particular situation, the discharge will take different rulings.
The Fiqh of It
Any discharge that exits the vaginal opening, whether clear, yellow, or white will nullify one’s ablution (wudu). The colour is considered when the discharge is fresh, and not after oxidation.
In order to pray, a woman has to first ascertain whether there is discharge on her sanitary liner or undergarments. If the impurity is smaller than the concave of one’s palm, the prayer will be valid, but disliked if it is not removed. If the amount of discharge is equal to or more than the concave of her palm, she must change her undergarments or place a fresh liner. If the discharge is continuous, she may use a piece of cotton (kursuf) or interlabial pad to block the discharge so her wudu remains intact. See ‘Using a Kursuf‘ for further detail.
If a woman sees yellow discharge only during her habitual days, it will be hayd. However, if a woman regularly sees yellow discharge throughout the month, it will only affect the validity of her wudu, and will not be counted as hayd. When the discharge becomes darker, it will mark the beginning of hayd. When it returns to the yellow she normally sees, it will signify the end of hayd. If the total days exceed the maximum for hayd, she will revert to her habit.