You welcome
If I have to change standard bulbs, I think I will go for nightbreaker. But I have not a lot of experience/done tests withs a lot of bulb.
It's hard to become a little bit blue with halogen because the base is yellow-white, not white blue.
Blue coating on glass of halogen is only to remove the yellow tint, but you can't reach color temperature of HID.
With a stronger blue filter you will lose a lot of intensity.
To be as blue as possible, try to choose bulbs with color temperature as high as possible. Color temperature is expressed in ° kelvin. 3200°k is standard recent halogen, 4000°k is a high efficiency halogen, 4200°k is the best you can achieve in halogen I think.
But be careful, a higher °k mean an hotter filament, and the life can be really short....
4500-5000°k is the really nice HID color, but it come with the help of lenses too - my old Mk2 Punto had a bit of blue even with standard halogen
Hope someone can help you to choose the best bulbs