Is it obligatory to stop praying and fasting when colored discharge appears before menstruation due to the use of hormone regulators? And is the fast valid if this discharge appeared and was not attended to?

These discharges that precede the clear menstrual blood are not considered menstruation; rather, they are istihada (non-menstrual vaginal bleeding), which necessitates performing istinja (washing the private parts) and wudu (ablution) for prayer. Consequently, your fast is valid, and you are not required to repeat it.