Gray is a classy choice. While color pops, accents, or blue anodization can be fun; that kind of stuff can look out of place in a more conservative environment. I feel the same way about coated blades and black hardware. Keeping with traditional metallic colors on the metals is a safe bet.
For inlays, overlays, or scales on liner locks; natural wood is a good choice in conservative environments. A good Micarta can also work well, provided it keeps to more conservative color choices like green or brown. This kind of consideration is a bit like choosing suit colors.
