Blue ink vs. Pink ink?!

Mercedez • Mommy to Leilani Ava Casnova born 4/4/15. 🎀💕 Pregnant w. My Boy—hoping for a healthy 9 months🤞

Can someone please explain why pink ink is better than blue!? I've been seeing it a lot while I'm skimming threw some people's post. I have also seen that the digital test aren't good to use. Why?