I would like to set the color for a series to be rgba(255,255,255,0), but this is messing with the borderColor for tooltips.
See: http://jsfiddle.net/j6Udd/1/
If you hover over Series 1 first the tooltip borderColor is the same as the series color. However, once you hover over Series 2 (alpha = 0) the borders for all tooltips and all series are completely transparent from this point on. I would assume the alpha designation should only affect the tooltips for Series 2..
-Chris-