So, DH and I are struggling to decide whether to have a fourth (and final!) baby. We DTD this month about 5 days before I O'd, no contraception. First question - sperm survives about 3 days doesn't it, not 5?

So, just for laughs, I did a POAS yesterday afternoon. I O'd about 7 days ago according to my CM and we have not DTD since the time 5 days prior (have been away and have had random children in our hotel bed each night and the others in a bed a metre away! No such thing as a romantic holiday with 3 kids!!). The POAS was negative, but I left it on the bathroom bench. I just went to tidy the bathroom and noticed a second line. It is feint, but definitely there. But it is purple, not clear like evap lines I have seen before. It's a FRER. So, second question - are evap lines ever coloured?? TIA.