When the Moto Mod Power Pack was first mentioned in MWC 2017 several different colors were shown. So far only the black version is available in the USA. However, I think this will change soon as there is a Moto Maker for the Chinese Motorola website which has customization of the slim battery mod.
The custom Moto Style Shells and batteries are both are available from Motorola in China here. They are both made by the same company, DIYThinker and use digital printing. Perhaps in the future there will be digital printed wireless charging mods and pads.
This sort of customization is similar to the Moto Maker of old and perhaps it will return. A customized battery mod that is usable across different generations of phones makes the additional cost incurred not seem so bad. If they can make this available for the holidays then it can make a nice present.