Alternating Row Colors for Dark Mode (XDEV17206)

We ported a big Xojo project to MacOS Mojave recently and in that process needed a good solution to update our alternating row colors for the listboxes. We used to have the usual code with row mod 2 = 1 and picking a color for every second row. But this is not perfect with a fixed color when the user can switch between light and dark modes. And while the average user does that while using the application, beta testers, of course, do that. So we needed a good solution for the project.