When a pregnancy test turns blue and blank this is called the linea migra. This may mean that your pregnant although the test are usually bot accurate so to be sure go see a doctor to run a proper and more knowledgeable test.
Your hcg levels are probably low or you are testing too soon. Maybe you need to wait a couple more days till you you re test again. I got a 2 pink lines one was faint the other dark pink and I am now 3 mos. Pregnant lol