honestly, I think the real problem is that the wiki says one thing, but due to other arbitrary reasons the tag is used in the wrong way.
Silver is literally gray, but with a metallic shine.
as well as gold is yellow with metallic shine,
the wiki clearly "overlap between this tag and the grey hair and white hair tags." this is a perfect match for silver, gray with a glossy finish
if it is gray (no matter if it is dark or light) and has brightness, it is silver.
otherwise, it is just standard gray, under this premise silver in my humble opinion is a valid color.
however, the big problem is when you add other colors such as light blue, bright white, or even bright light brown.
here it is quite easy, add the tag (insert any color)_hair + shiny_hair
you don't think that's enough? well, we can use a tag simply called "platinum hair".
just platinum, so when a character with hair as shiny as metal appears he can use this tag, regardless of the color of the hair, be it blonde, gray, white, blue, light, etc.
or if they want a more extreme solution, they can change the name of the silver hair tag to platinum hair so the current mess is solved for a second.
now, before you say "young characters can't use the gray/white hair tag" please read to my humble opinion
that a character is "young" is not enough reason to someone not use the tag gray/white hair and use silver instead, that is a very arbitrary and not objective reason. oh come on, we are tagging the hair color to facilitate the search, the hair colour has nothing to do with the age of the character.
it's like saying "I won't use the blonde hair tag because dumb characters have that hair color and instead I'll use orange hair instead", regardless of how light/dark the character hair is. sounds arbitrary and unserious, doesn't it? the same applies to silver hair.
this is my sincere opinion, it is true that I am nobody to force you to follow my opinion.
but, if we all agree on which rule to use, this current mess with silver hair can be solved easily, but with such an arbitrary use as young characters not being allowed to use the gray/white hair tag and allowing it will not solve anything, it will only make the problem worse, no matter how many tags indicating brightness are used.
TL:DR: the current problem is that this tag is used to represent hair of any color with metallic sheen, and it is used as a perfect excuse not to put the gray/white hair tag on a young character. the solution is not to kill the tag, the solution (in my opinion) to be used strictly are the shiny gray and the other colors use shiny hair