Verkkoa vague result might indicate a very faint positive pregnancy test or even just an evaporation line. In this article, you’ll learn how to tell the difference. Verkkohere's how to tell the difference between a true positive pregnancy test and an evaporation line, plus tips for avoiding an evaporation line on blue dye. Verkkoif hcg is present, then the second line, the “control line,” will turn pink or blue. The average test takes about three minutes to show signs of a positive pregnancy test.