Apple has been granted a patent for color-changing Apple Watch band that would be controlled with an app.

According to Patently Apple, the U.S. Patent and Trademark Office officially granted Apple the patent on Tuesday.

The filing, which is publicly available on the government website, details how the technology would work. The band includes electrochromic features that provide adjustable color control based on an applied voltage to offer a variety of colors and color combinations to be displayed by a single band. Through a system, presumably an Apple Watch or iPhone interface, users can control, select, and/or adjust colors of the watch band.

Electrochromic material is best known as the technology behind anti-glare mirrors in cars and smart glass windows that regulate heat and become tinted or opaque. The patent describes how the filaments or fibers of the band can include conductors and electrochromic layers that that respond when voltage is applied. The filaments are then woven into fabric like any normal cloth band. Diagrams show three stripes of fabric that can independently show different colors.

The patent also explains how the color can be manually changed by the user or adjust automatically based on time, date, text, icons, and notifications. So your watch band might turn a different color if you get a new text or your alarm goes off. So, kind of like a highly sophisticated mood ring.

It's a pretty remarkable achievement to weave this technology — that's used mostly in glass — into fabric. But it's worth noting that a color-changing Apple Watch band might never come to market.

Apple and other big tech companies have moonshot research and development programs that often file patents that never come to fruition. Plus, interchangeable bands for Apple Watch are lucrative for Apple and provide opportunities for brand collaborations.

That said, Apple recently received a patent for a built-in smartwatch camera, so these patents might be the seeds of some major changes to come with Apple Watch.