Evap lines

Laura • I am 34 and have a 2 & 3yr old. DH and I struggled with infertility for several years and had a successful IVF with DD.
If you are like me I POAS, wait then basically stare at it till my eyes cross hoping to see the faintest line! Yesterday I took a test with blue dye and it showed a very thin blue line in the result box. I thought it was an evap line since I have heard blue dye is notorious for this. I used my last blue dye test and could swear I saw another faint line. Took 2 FRER and they were neg. Do evap lines show color?