Support was unhelpful, but eventually I figured out it was a browser cache issue.Selecting every single option to clear cache/temp files, etc in Chrome did it for me.
I have the same situation exactly and I cannot find a reason for it. Edge works well though. I'll raise a support case with ServiceNow and post the results.
Hey, Had the same requirement, and through trial and error found this works well on my copy of the original style in the sys_ux_style table:"--now-color--neutral-18": "255,0,0",