Metals exhibit their characteristic shinyness as the delocalised electron sea in the metallic bonds are able to absorb and re-emit photons over a wide range of frequencies. Thus the reflectance spectra of most metals appears fairly flat and they appear silver in colour. I first thought that it may be something to do with the single unpaired electron in the outermost valence shell, but Silver also displays this but has a flatter reflectance curve.
Chemists often consider the first sub-shell of a given angular momentum to be anomalous.
The 3d, filled in copper, is less shielded by the s and p subshells than you might otherwise expect. Silver, with a filled 4d behaves more like you think it should. So gold also behaves somewhat differently. If you were to do a solid state calculation on gold without including relativistic effects you would predict it to be silvery. Including relativistic effects you get reasonably good agreement with reality.