All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
First, all perfect praise be to Allaah who guided you to Islam and we ask Him to bless you with religious knowledge and make you firm on this religion until you die.
As regards your question, the first pink discharges that a woman sees before the beginning of her menses blood, these discharges are considered as menses if they coincide with the period during which she usually gets her menses, so she should stop praying or fasting. In principle what a woman sees at the time of menses, like blood, a yellow discharge or a pink discharge is a menstruation even if there is no blood prior to it. This is the opinion of the following scholars: Abu Haneefah, Muhammad, Maalik, Al-Layth, Ash-Shaafi'ee and others.
Ibn Al-'Arabi from the Maaliki school said: 'The scholars differed in opinion about the pink discharge, however, the scholars that are mentioned above, are of the view that this discharge is considered menses - if it is during the period of menses - even if there is no blood discharge prior to it.'
To conclude, when a woman sees a pink discharge she stops praying if these discharges coincide with her menses, especially if she feels pain or colic that a woman usually undergoes at the time of menses.
Allaah knows best.