I've found a solution to this issue.
Following from the newly added documentation, https://developer.apple.com/documentation/bundleresources/information_property_list/nsaccentcolorname
While you can set this directly in your Info.plist, the recommended approach is to use the Global Accent Color Namebuild setting (in the Asset Catalog Compiler - Options section) of the target. Set the value of the build setting to the name of the Color Set in the asset catalog. Xcode automatically sets NSAccentColorName to the appropriate value in the Info.plist file when building your project.
It looks like Xcode automatically adds the NSAccentColorName key to watchOS plist when building. To avoid this, I've unset the ASSETCATALOGCOMPILERGLOBALACCENTCOLORNAME on the Xcode build settings for my watch os related targets. Since I use xcconfig files, I set ASSETCATALOGCOMPILERGLOBALACCENTCOLORNAME = , i.e. empty, in my parent watchOS.xcconfig file.
Topic:
App & System Services
SubTopic:
Core OS
Tags: