Light Gray Hair
Q: I went gray at an early age, I am 60 years old. My hair has been light platinum for a long time. I would like to go back to a light gray. What color would I use to get that gray look?
In most cases, your best bet is to use a haircolor as close as possible to your natural gray (generally something with a blue or blue-violet base) after the color stripping and use that (in a demi-permanent formula so that it washes out gradually) to blend your hair until your natural gray grows out completely.
You may also want to look into using a temporary color rinse to brighten the tone of your hair, instead of using demi-permanent color. You can usually find a rinse that is made to brighten gray hair (such as "White Minx" by Roux).
You have to remember that rather than actually being a "color", gray hair is actually hair that is lacking any pigmentation at all. This means that getting a truly "gray look" means you have to strip out ALL of the color in the hair, which can be VERY damaging.
Your case may work better given that you are purportedly working with fully gray hair and a very light shade of artificial color, but please use caution and follow all the directions for the products you use carefully.
How to color hair
Can I use a product to remove my hair color and go all grey at once?