Depends on your class.
Engineer is no color at all.
See the uniform guide here:
http://bitterstonethunderers.shivtr.com ... nread=true
Everyone else is necron abyss. But not simply all pieces necron abyss. That is pricy and not very shiny.
Be creative.
You Can combine it with other colors.
IB use also Ice blue on some shoulders as second Color that the runes shine in a blue light or use lots of Dark metal tones and gold or bronze at the edges.
If you have an shield change appearance to the one with the blue front and the winged hammer on front.
Runi and slayer also use necron abyss and then different colors that the runes shine out.
Memo to me: overwork uniform guides.