I colored my hair 6weeks ago a medium red blonde, can I color it now a light auburn and how will it look

Yes you can color it but be careful with reds as they tend to get brassy, sometimes can even turn greenish. If you are going from darker to lighter you may need two boxes of hair dye because your roots will def grab the lighter color but the ends where the old color is may not grab the color as well you may need to use more on the ends,, I would suggest going to your local salon/stylist and getting a consultation.