A sample demonstrating how to obtain the background color that apps should use from a simple Win32 process, using only C++ and the base Windows SDK with no additional library support (such as C++/WinRT or WRL).

BackgroundColorSample.cpp

#include <windows.h>
#include <roapi.h>

#include <iostream>
#include <cwchar>
#include <string>

// For Windows.UI.ViewManagement.UISettings
#include <windows.ui.viewmanagement.h>

int main() {
    ::RoInitialize(RO_INIT_MULTITHREADED);

    HSTRING_HEADER header;
    HSTRING hstring;
    ::WindowsCreateStringReference(
        RuntimeClass_Windows_UI_ViewManagement_UISettings,
        wcslen(RuntimeClass_Windows_UI_ViewManagement_UISettings),
        &header,
        &hstring);

    std::cout << "Activating UISettings" << std::endl;
    // TODO: Use an RAII container/wrapper (such as Microsoft::WRL::ComPtr from the WRL library) to prevent leaks.
    IInspectable* uiSettingsAsInspectable = nullptr;
    HRESULT hr = ::RoActivateInstance(hstring, &uiSettingsAsInspectable);
    if (FAILED(hr)) {
        std::cout << std::hex << hr << std::endl;
        return 1;
    }

    std::cout << "Querying for the appropriate interface..." << std::endl;
    ::ABI::Windows::UI::ViewManagement::IUISettings3* uiSettings = nullptr;
    hr = uiSettingsAsInspectable->QueryInterface(__uuidof(uiSettings), reinterpret_cast<void**>(&uiSettings));
    if (FAILED(hr)) {
        std::cout << std::hex << hr << std::endl;
        return 2;
    }

    std::cout << "Asking for the current background color..." << std::endl;
    ::ABI::Windows::UI::Color color;
    hr = uiSettings->GetColorValue(::ABI::Windows::UI::ViewManagement::UIColorType_Background, &color);
    if (FAILED(hr)) {
        std::cout << std::hex << hr << std::endl;
        return 3;
    }

    std::string colorName;
    if (color.A == 0xff && color.R == 0 && color.G == 0 && color.B == 0) {
        colorName = "Black/Dark";
    } else if (color.A == 0xff && color.R == 0xff && color.G == 0xff && color.B == 0xff) {
        colorName = "White/Light";
    } else {
        colorName = "Other";
    }

    std::cout << "Current background color is " << colorName << std::endl;

    return 0;
}