A white scorpion is simply a regular scorpion that has shed its skin. All arthropods must shed their skin so they can continue to grow. As the new skin continues to grow, it darkens and hardens.
When a scorpion sheds its skins it becomes vulnerable to attack by predators. The shedding of its skin exposes softer skin which makes its body easily penetrable. The scorpion still has its stinger as a defense, but its legs can become stuck in the old skin making quick movement difficult.
Most scorpions in the United States do not pose a lethal threat to people they sting. However, there are species in Africa and the Middle East that have extremely poisonous venom.