A scar can take up to 1 year to lose its color and turn white. That said, some scars turn into keloids which will remain red unless treated with cortisone injections &/or laser. I would have your treating physician assess the scar to make sure its healing properly. Also, fair skinned people have red scars for longer usually than those less fair.
Scars mature and redness fades for a year or more. Longer in children or those with a history of hypertrophic or keloids in my experience. To learn more about best ways to manage scars to minimize their present see below link.