It's the strength of lacing that I feel everyone should be striving for with exhibition blues. The standard here calls for the blue ground colour with each feather laced with a darker blue. The thickness of lacing isn't suggested, but I think a stronger lacing over all on a good good ground makes for a much more striking impact.
Dark blues usually do have a stronger lacing. It has always been the lighter blues where lacing is harder to achieve. This is why breeding top quality blue orpingtons is so hard to do. I believe that like most other laced birds, to acheive optimum colour in both sexes you need to breed from a male breeding line and a female breeding line. I'm putting this into practice and I hope in the next few years it will work out for the best.
Matt