I think best way is not to give it a thought, but to find images in the ww web. Here is one, you also have posted one in ifrst entry of this thread.
When I look at it it could be done by starting with a good ultramarine blue. Maybe primer it white and then get a thin layer/wash of blue on it. It has to be a bright blue. Use the smae blue for OSL on tunica. I guess I would try to use most of the blue on tunica and 99% white on bolt.
In the photos the most part of the lightning is white, just small areas on the edge are blue.
I don't see any danger of getting it to look like an ice bolt. The form of the bolt and the use of blue will help too. Stay away from using any greens though.
If I would paint ice I would start using turquoise first layer and adding light green, dark blue and white to it.
