Confirmed fix works on Android 15, thanks!
Use the following script to add in the sample StatusBar to test that the visible navigation bar transforms normally on Android 15.
Also works on Android 15 when removing window.setNavigationBarColor(), so you might want to check again to test this? After all, the latter was deprecated on API 35.

It's so weird that it doesn't work before Android 15.

local colors = {
    {1, 0, 0}, -- R
    {0, 1, 0}, -- G
    {0, 0, 1}  -- B
}
local colorIndex = 1

timer.performWithDelay(1000, function()
    native.setProperty("navigationBarColor", colors[colorIndex])
    print("rgb", unpack(colors[colorIndex]))

    colorIndex = colorIndex % #colors + 1
end, 0)