V6 I prefer, Black text is easily readable and overall looks good. Perhaps give the text a little bit of a shade around it so it can be readable more easily, V5 would take the second place...
I choose V2. Just do something with the font color and the background color.There should have a color harmony.
I prefer V6. I like the design because the ball is centered with in the stripe and it looks a little more organised than the others.
I would choose none of them. Choose right colors. Do not use red text over red background! Do not use yellow text over white background!