The leniency of being found on a colored surface only applies to stains found externally. Since the diaphragm was inserted internally, any blood found on it is treated strictly, as with an internal bedikah. Therefore even a small amount of reddish, black, or dark brown blood found on a colored diaphragm would render a woman niddah. Discharge of an acceptable color – such as yellow, white, or light brown (like the color of coffee with milk), with no reddish hue – may be disregarded.
A woman is not required to look at the diaphragm for any staining after removing it. She should wash it off without looking (she can close her eyes or turn off the lights if necessary) to avoid finding any stains.
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