I always thought evaps were supposed to have no colour?

When I took this test 2 days ago it sort of looked like there was a line but I brushed it off and forgot about it. I know you’re not supposed to look at a test after the window - and I also know these tests suck (although this is the brand I got a BFP with for my daughter)

So my question is - why is this very clearly blue? I thought evaps were colourless?