If you fish a longer windon leader or topshot, it probably does not matter. On a short leader, such as the 2' I use, I think it does matter. But everyone has their own opinion. Some think it does not matter at all regardless, as they are working topwaters exclusively, and fast. So they feel visibilty to the fish is not an issue because the line is not in the water. However, I throw subsurface baits also, so my line is in the water. And no matter how fast I work a topwater, the line will be in the water now and then. White and any other spectra line color for that matter is highly visable in the water. Also, the blue is not hard to see from the boat, looking down. I would not say its high vis, but you can see it better than you can see mono.
I remember reading an offshore article by Pat Lemire (in Texas Fish and Game I believe) where he says he actually uses white spectra and then uses a marker to color the first few feet blue to camo it up. Of all the colors, I believe blue is most difficult for fish to see in the water. JMO though.