There are a range of generic leather care products you buy. For example, Furniture Clinic Cleaner & Protector and Furniture Clinic Recolouring Balm (Tan) available form amazon.
Unless there is damage or fading we'd recommend only using the neutral cleaning and protection products rather than a colour restorer.
Always with leather products and coloured treatments, you should use first on a small test area that won't be visible to ensure compatibility and colour match.