Header Overlay Greyscale Slider

From the image you can see I was able to add a “Greyscale Slider”.
This only reqired changes to 2 arrays:

“$septera_defaults” and “$septera_big” in admin > defaults.php & options.php respectively

and a change to the “grayscale filter” in includes > custom-styles.php.

This enables the degree of greyscale and accommodates both the current and prior behaviors for the “Header Overlay Opacity”.
So it would be nice to add this to the “Customizing . colors > Header” panel.