I would suggest a Liver of Sulfur patina
Colors develop one after the other: gold, green, pink, blues, purples,
grays and finally black. If the water is warm or the metal is warm,
the process is greatly speeded up. When you are trying to achieve a
specific color, the cooler the water, the more likely you are to lock
in the color you wanted. The way an item is dipped will also make a
difference. If an item is dipped sideways, the colors will be
streaked. If an item is dipped face down, more vibrant colors will
appear there than on the other side. If an item is turned over and
viewed after dipping, (but before neutralizing) the colors will
continue to develop and often will pool in places, leaving a mottled
It is a method that is quite simple to use, although it takes a bit of experience to get the desired color correct. The patina is only on the surface, requiring no changes to the actual composition of the sword. A caveat would be in any alloys that are used in the silver to strengthen it, reacting differently to the chemical.
To highlight the effect, microgrooves could be made throughout the sword surface. These groves would produce angled surfaces that would reflect light in different directions. If they were concentric, the effect would be to focus them and highlight them when looked at from a particular perspective. Potentially bright flashes of gold color on a silver background.
But a digression here - the photons 'reflected' from a surface are NOT the same photons that are incident to it. The incident photons are absorbed by the material, and re-transmitted. Usually, this is instantaneous, but the process can be delayed. Also, in some cases such as fluorescence, the incident UV photons are re-transmitted at another frequency. There is no quantum necessity for the re-transmitted photon to be exactly the same as the incident photon, if the substance can either supply energy or absorb energy such that the re-transmitted photon has a different energy level than the incident photon.
"The quantum dot can act as a true single photon source," says
Srinivasan. "Each time we excite the dot, it subsequently releases
that energy as a single photon. In the past, we had little control
over the wavelength of that photon, but now we can generate a single
photon of one color on demand, transmit it over long distances with
fiber optics, and convert it to another color."