Let's say a person is minorly colorblind, as they failed one or more of the Isihara Tests. How can they determine if they are disqualified for mareh's, examining bedika cloths? If they can see red and they see brown, but when they examine cloths it's hard for them to distinguish between red and brown stains, how can they clarify if it's due to a lack of experience, or due to their colorblindness? Is there an objective way to determine this? I asked a posek and he wasn't sure (unless the person literally can't see red, which we're not discussing).