If your marquee image looks too dark, you can easily change the overlay color.
- Once you're in Customizing the Theme, on the left click on colors (if you don't see colors, simply click on the marquee image and you'll see the edit options on the left).
- Click on the color next to where it says "Marquee Overlay Color"
- Click the color wheel on the bottom:
- Slide the transparency bar all the way to the left, then click Save and you'll be all set!