HELP my sister in law wants me to make her cake for her 25th wedding anniversary and she wants it silver how can I achieve that color? is there silver food coloring cause I haven't found none. so should I do buttercream or fondant to get the color just right? she said its my call on fondant or buttercream

AUnless you're going to use edible silver leaf, you'd need to spray it on. Spraying edible silver on the whole cake isn't that pretty in my opinion. It will also emphasize any imperfections or irregularities in your work.

I'd see if they would consider silver accents.

You can buy silver sprays in a can even if you don't have an airbrush.