There really seem to be several shades of pale when it comes to seaglass. Here is a glimpse at some of the lighter and whiter pieces I have been wire wrapping recently: I have not played with the colour in the photos. All the specimens were found on Dublin beaches.
Pale aqua and seafom seaglass pendants
None of the above are exactly 'white seaglass' as they all boast aqua or seafoam undertones. The greenish, seafoam shade is caused by the iron content of the sand used to manufacture the original glass. Though I often see very pale shades like the one on the left being called seafoam, I wonder if 'white-washed' wouldn't be a bit more accurate.
The second from the left has more than a tinge of bluey-green to it, which comes up even deeper and richer in low lighting.
White seaglass ornaments or pendants
Above are examples of true white seaglass for comparison purposes. If you'll grant me one pun, the difference is clear.
To learn about shades of BLUE seaglass click: HERE
To learn about shades of GREEN seaglass click: HERE