Why did I mainly use blue oil pens when I was a child, and now I basically use black gel pens?

Children are naughty and often get pen water all over their hands and books. Blue looks cleaner, and black ink is used for printing. Blue is clearer on paper, and it is easy to see the pen at first. We can also use black at that time. But black carbon ink is easy to block the pen. Especially when I was a child, my pen was poor and my ink was poor. I thought that was the reason.