Mazal tov on your upcoming marriage!
White undergarments are worn during the
clean days so that discharge will be apparent. You should inspect each pair of white underwear at least once, before putting it in the laundry, to check for stains.
Stains on underwear are halachically significant only if they are larger than a
gris (about the size of a US dime or an Israeli shekel). A stain of this size would be easily noticed, and there is no need to look for anything smaller. (Note that this is different from discharge found on a
bedikah, where even a small amount is significant.)
Brown the shade of coffee with milk or lighter, with no reddish tinge, is not a
niddah color and does not affect the clean days.
We follow the position that it is permissible to wear white pantyliners during the clean days if you need them for comfort. Stains found on a
disposable pantyliner do not have halachic significance and would not invalidate the clean days. There is no halachic requirement to inspect disposable pantyliners.
Please let us know if we can be of further assistance.
