My Application is in dark mode... I want to undo that .. is there a setting within Xojo building for this?
I can't read my text on windows in dark mode.

App.SupportsDarkMode

But you better check the text color to be correct.

If you don't change the text color at all in the IDE it will automagically support Dark Mode.
Fighting against dark mode is not the way to handle things.

Edit: Building with the Supports Dark Mode flag off can help for now, but there's no telling how long Apple will allow that plist flag to operate. Should they suddenly decide to remove the ability to disable dark mode your app will be unusable overnight.

Where is that build flag?

@Edwin L I don't think that is how it would work. Some apps would work best in Dark Mode but probably toggling games from dark to light or vice versa might not be good. You can always still keep your color schemes a shade away from the extreme white and black to prevent it from toggling if they stop supporting the plist entry

<key>NSRequiresAquaSystemAppearance</key>
<string>true</string>

Note what Apple says on this page:

https://developer.apple.com/documentation/appkit/nsappearancecustomization/choosing_a_specific_appearance_for_your_app?language=objc

@Jason P Note what Apple says on this page

Supporting Dark Mode is strongly encouraged.

That's Xojo's SupportDarkMode=true, resulting in an app that support both light/dark mode.

Use the NSRequiresAquaSystemAppearance key to opt out temporarily only if you intend to improve your app's Dark Mode support.

That's what Xojo's SupportDarkMode=false does currently, right?

If you do not plan to support a dark appearance at all, apply a light appearance to your entire app, as described in Assign a Specific Appearance to Your App.

And that seems to not be available in Xojo yet - maybe worth a Feature Request?
The way I understand apple's docs, Xojo should not just have that boolean switch SupportDarkMode, but a way to choose:

• Supports both Light/Dark Mode (strongly encouraged by Apple)
• App is entirely/always Light Mode (not planned to support Dark Mode)
• App is entirely/always Dark Mode (not planned to support Light Mode)

That would cover the following part of Apple's Docs:

You may choose which appearance—light or dark—to adopt for your entire app (or for specific views, windows, or popovers).