My Valkyr prime is:
A Blue from Shamrock for the Primary
Black for Secondary
Orange (non-Shamrock, don't want too much saturation) for Tertiary
Greenish (for a copper, rather than gold look on the shiny metal parts) for Accents.
...and I think the brightest red I had for the energy color.
IMO the key for a good Valkyr Prime look is a nice contrast between the Primary and Tertiary, with a Secondary that's darker than both. as MajesticPinecone says, her Prime armor has a lot of areas that are just one color, so you really want the designs the Tertiary areas form to really pop out without clashing with the Primary.