Unfortunately, you cannot easily adjust the details like the duration of the fade in or the colors, and also there is no fade-out included that would be great too. I hope that luman will implement something like that in the next version of his extension.
Also, another little thing that I noticed is a small positioning bug that animates the window on the top left and then positions it on the last saved position. This shouldn’t be a problem for applications that open in full screen of course. Whatever the case, this is an interesting extension that needs your feedback to become better.
To add the fade-in effect for your windows, simply turn the switch to “ON”