Dark Boot helps you customize the appearance of various elements of the operating system. The tool has a very attractive interface, consistent with its purpose of making MacOS look better. Conveniently, there are tabs that allow you to go straight to the desired option. In fact, the tool is so straightforward that I do not think anyone will have problems to use it, even if it is the first time.
The first tab lets you change the color of the boot screen. Four basic options are possible here: you may keep or go back to the default color, choose black or gray, or select a custom color. Then, you can click on Apply. You should also know that for the changes to be enabled, two reboots are required. The second tab is also intended to customize the boot screen, but, in this case, it focuses on the boot image. Again, you should browse for the desired image and apply your changes. There are restrictions as to the size of the loaded file; besides, only PNG and JPG are supported. The following tabs let you customize your Login and Lock screens. There is not much difference in terms of the procedure to do so, except that, in the case of the Lock screen, you can also use a custom lock message.
All in all, Dark Boot does not belong to the list of those indispensable tools. In fact, what it does is kind of superfluous. Yet, it provides a way to personalize your operating system at no cost. I must alert you that, although it did not happen to me, some users have complained of booting problems after using this app.