That sounds like a great modification to the MKS tanks in FS25! The increased capacity will be very beneficial for players looking to transport larger amounts of liquids, and having the option to choose from all the colors available in the base game adds a nice customization feature.
Having the base price set at €20,000 for the smaller tank with a capacity of 8,000 - 24,000L, and €70,000 for the larger tank with a capacity of 32,000 - 128,000L seems like a reasonable pricing structure considering the increased capacity and customization options.
Players will likely appreciate the flexibility and versatility these revised MKS tanks offer, allowing them to better tailor their equipment to match their specific needs and preferences. Overall, this is a great enhancement to the game that adds more depth and choices for players to enjoy.