Based on what you write, that staining has been limited to colored undergarments, you are not currently considered to be in niddah. In this situation, we would recommend abstaining from relations until about a day after the staining subsides. Please note that this is a precaution against a flow beginning during relations and not a strict halachic requirement.

Staining is fairly common during the first cycles of hormonal contraception as well as for women who have changed pill-taking patterns (e.g., missing a pill or extending the length of the active pill cycle). Even so, you may wish to consult with your physician about the staining.

If the staining does not abate, you may wish to consider (in consultation with your physician) ending the active pills early to bring on withdrawal bleeding and niddah for this cycle.

Please write back with any further questions.