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Basecoat the sword in hawk turquoise over black primer.
Blend the sword up to a mix of hawk turquoise and white, and down to black. Larger blacker areas for a darker look. More toward white for brighter. Cross the highlights on each section (light-to-dark-to-light as you go round the sword).
Edge highlight with the turquoise / white mix.
Paint fine y's and lines across each section of the sword.
Mix a bit more white in and apply sharper edge highlights at the tip and dot the places where the 'lightning' touches another line.
Good flowing paint, good brush control and a fine point brush are your friends for this.