Hmmm........maybe way off here, but it seems you would want a Roo from a white egg laying family (Campine, white/Brown Leghorn etc) to breed with your Hen that you think has the blue egg gene.
Since green eggs are just tinted eggs with the the blue gene layed over them. Seems like you would have a better chance getting truely blue eggs if one of the parents carried the white gene rather than the brown gene.