If I'm showing western, I go with a silver halter. English, either my snaffle bridle or a plain leather halter. In my area, an exhibitor in western attire with a plain halter won't place against an equal western entry with a silver halter. In English attire, silver is a no-no.
That being said, clean and well fitted is paramount. You can have the most expensive, silver-laden halter in the catalog, but if it doesn't fit it doesn't matter.
Personally, I like dark oil show halters, and IME that has been the fashion in my area. There are some colors of horses that are a bit more flattered by light oil - palominos, some greys, some paints, some shades of dun.
A stubborn horse walks behind you, an impatient one in front of you, but a noble companion walks beside you ~ Unknown