This description will be expanded but is at present quite usable.
--------------------------------------------------------------------------------------
It is quite possible to alter the Opacity of all the Cells in Fast Dial 1.x
To do this one makes use of a very useful Firefox Extension called Stylish.
There is a short introduction to Stylish here
To simply download Stylish from the Mozilla Add-Ons page go here.
The best site for finding Styles to use in Stylish is called Userstyles
At the moment there are a couple of Styles on the Userstyles Site that will enable you to alter the Opacity of your Fast Dial Cells
Style 1 enables one to change the Opacity of All Cells in Fast Dial 1.x.
Also it allows one to alter the Opacity of Dialling Cells Seperately from Group Cells.
Style 2 is eactly the same as Style 1 but it has the added possibility of altering the opacity of your cell when you hover over it with the Mouse.
.