I think color is a very good choice. As far as I understand, you are dealing with only two states, not initialized and initialized. In this case, you only need to flag the risky state, let's say not initialized.
It also depends on how far away you want this to be visible from and the size of your screen. The smaller the screen and the further away you are, the larger the colored area needs to be. You can experiment with small UI elements like a status icon and move to larger ones like window border, title bar and ultimately background color.
While using color, make sure you account for the color blind population, men are generally more affected than women. Here are some good resources:
Another advice when using color is to associate it with another visual feature, to make sure color blind people are not left out. In your case, position is a good choice. For example: