L'Oreal Superior Preference did nothing...

I am naturally blonde and wanted to try out a different colour! I saw this product on the shelf and picked out the shade named "Stockholm" which is a silvery gray colour that looked really nice. I followed the instructions and my hair kinda looked slightly gray-ish for about a day and has since already faded out a couple days later. I used the colour protect conditioner that came with it in the box but it hasn't done much.