The secret to the light-colored potato chips is the variety of potato used by the larger potato chip producers. They use any of several ‘Chip’ stock varieties. These high-solid, low-sugar utility-looking potatoes are generally not available in retail stores. From your description you’re likely now using a russet variety, which is higher in sugar content. The low-sugar chip varieties do not darken, or caramelize nearly as much, while the russet varieties will be a noticeable darker color chip after frying. This is a matter of preference, and many independent chip manufacturers use a russet successfully even though the final product has a darker appearance. Both chips taste great, again it’s just a matter of preference. The chip variety used by manufactures are generally not available to the public and many varieties are proprietary. However, if you have access to a local foodservice distributor the produce buyer may be able to sell or procure a chip-variety for you to try.