Evap lines

I’m just curious, how common are evap lines? I have had several tests that have major squinters within the first few minutes l. I’m talking have to make sure it’s in the right light really second guessing if it’s really there. Then they get darker after 5-10 minutes. This has been with different brands and different types of tests, all pink dye though. I honestly can’t tell if the line has color or not. My line hasn’t gotten any darker in almost 1 week so I’m just curious if they are most likely evap lines. I’m 5 days late just for reference.