Unlike classic PPM user interface css themes, the new UX offers one clean new user interface color palette by design. Until the new ideation process can prioritize further color configurations, here are a couple ideas.
In Chrome, you could add a High Contrast extension, and then make more subtle color palette adjustments with the Color Enhancer extension. Attached below is an animated GIF showing the default, an enhanced color contrast mode, and inverse mode. The Color Enhancer would let you change a blue button to green. Other browser accessibility extensions, custom CSS, coding, or personalized color changes at the browser or OS level might also change the appearance.
The obvious disclaimer here is that we can in no way support or even know what your users might be doing with color palette changes here. So if you read the documentation, the examples will show the default color values. If you call Support, the first thing we might suggest is disabling any extensions. It could also present challenges for your users if one tells another to search for two similar projects and choose "the green one" when another user has changed their palette settings making it blue.