color overlay featured image

Hi there,
I need some help with Vaaka theme Version: 1.0.0 by Sami Keijonen, I hope someone can help me. Is there a way to make some color adjustments to the featured images? There is a already a mouseover opacity effect installed in the theme and I want it to adjust the foreground color of the image itself before mouseover. I think I must change the background color of the foreground picture which is used for the opacity effect on hover, but I cant find the settings.