I've nickel plated several hundred guns, I've yet to see any one of them with any yellow hue. Maybe those that have, have had it done with some other chemical composition. Ask any of the shooters here, that have had the plating done by me if they see any yellow or any other color, besides silver.
Nickel does reflect very well and if you're wearing a red. blue or other color shirt, it may reflect that color. A satin nickel will hold all of the sharp corners and turns in highly detailed engraving.
With regards to the nitriding, I may differ with others in regards to nitriding an engraved piece. As I stated in the other post, the metal must be polished after it comes from the oven. It is possible (and highly likely) that any detail in the engraving will be washed out slightly. Especially with engraving showing any relief..ie 3 dimensional engraving. This would also hold true for a polished nickel piece.
Nitriding will be a silvery color. How bright/glossy/shiney, depends on how much polishing/buffing is done. Remember..the more you work on it, the bigger the chance of breaking through the hard surface.
The gray look comes more from a satin chrome finish. Chrome will give you two colors, and three finishes. All of them involve the metal prep...polish/buff, polish, bead-blasting.
My personal opinion, for what it's worth, I don't care for the chrome. Not for what it is suppose to do, but for what some platers do not do. I get several guns in here each year that have the satin chrome finish. Each and everyone of them is poorly done. Some will still show bluing through the plating. Most still show ALL of the dings and scratches that were present before the plating process.
When someone says they have the best price, belive them, AND, believe me, you will get what you paid for. They just will not take the extra time to examine every piece for scrathes and dents, and still, will not take the time to remove them before plating.
As for who actually does the plating processes, 99% of any business(gunsmiths and dealers) do not do the actual plating. It is sent to a company that is in the business of doing it. Their chemical composition, and application is researched to give exactly what we're looking for.
The plater's job is just that...plating. How good it looks is determined by how well the metal was prep ahead of time, by the gunsmith or dealer.
But hey, everybody's tastes are different, and some can't recognize a quality, cared for job, from garbage, but are still happy.
Doug