* Permanent auburn dye: This will permanently change your hair color, even when it fades. It will likely lighten to a more reddish-brown shade, but it won't go back to your natural light brown.
* Semi-permanent auburn shade: This will deposit color on top of your hair, but it doesn't penetrate the hair shaft like permanent dye. It will fade gradually over time, and your natural light brown will start to show through. How quickly it fades depends on the brand, shade, and how often you wash your hair.
To get a better idea of what to expect:
1. Look at the box dye's instructions: They usually show examples of how the color will look on different hair shades.
2. Consider getting a strand test: This will let you see how the color will look on your hair before you dye it all.
3. Talk to a professional stylist: They can give you personalized advice based on your hair type and desired result.
Remember, even if you use a semi-permanent dye, it's unlikely to fade back to your natural color completely. It will likely be somewhere in between your natural color and the shade you dyed it with.