Mark out the shape of the lightning bolts with Calgar Blue . Use reference photos from Google for inspirations.
Paint a thinner line of Hoeth Blue within the lines established previously. Don't follow the shape perfectly, add extra waves within the line to make it more organic.
Go over random patches of the lines from the previous step with Ulthuan Grey . I would recommend going over roughly 50%.
With Dead White or a pure white of your choice. Go over some more of these lines where the Hoeth Blue still shows. Don't be afraid to leave gaps.