From Xojo Documentation
New in 2021r1.1
Displays the operating system's color picker.
On Windows and Linux, the operating system's color picker window is modal. On macOS, the color picker is not modal. This means that on macOS, the ColorSelected event will fire every time the user clicks on a color.
On macOS, if the Color Picker was left open when the user quit your app, it will be automatically closed upon relaunch.