Thank you for reaching out to us.
Yes, because stains on a colored surface do not make a woman
niddah. Though not required, colored sheets are recommended for use when a woman is not
niddah, so that stains found on them will not change her halachic status. (Learn more about the laws of stains
here.)
Colored sheets are most relevant for sexual relations or other times when a woman may go without underwear. In a pinch (as when a a couple is caught at a hotel without colored sheets) a strategically placed colored towel can often subsititute.
We hope this is helpful. Please let us know if we can be of further assistance.