Alternate Navigation / Header Bar

To the point: How can I customize the alternate navigation/ header? It defaults to transparent and then dark sticky on scroll. I would like to have light text with no background, but then have it go to the default sticky header. What is the easiest solution?

A second question (I won’t make another thread), is it possible to easily add a color overlay to a background image? It is getting tiresome to have to edit the photo with a tint and then re-upload it to use as a background.

Thanks!