Colours of the company that's been developing it, presumably the final version will be nasa / white color scheme

>Though this prototype uses a dark gray cover material, the final version will likely be all-white when worn by NASA astronauts on the Moon’s surface, to help keep the astronauts safe and cool while working in the harsh environment of space.

https://www.nasa.gov/feature/spacesuit-for-nasa-s-artemis-ii...

Apparently they are keeping that under cover for competitive reasons:

https://twitter.com/skrishna/status/1635998864531439617

According to the NYT article linked above, the final suit will be white for thermal reasons. This color scheme is just for the prototype.

And I imagine it will blend into the lunar background, which also seems like an odd choice.