Lighten a medium auburn to light

Go to a "sally's beauty supply " in your area. They have great do it yourself products and great staff to help you, or just go to a salon and take a sample color color of what you are looking for.

Is your hair already dyed or is it natural? If it's bleached, colored, or dyed, you'll have to use haircolor remover first. Then, you can bleach or dye it.

If "light" is more than 2 levels from your natural color, you'll have to use bleach first and then tone it. If it's within that range, you can use a single-process haircoloring.