How do I make the slider images appear in their native color without the gray overlay?

1. Please activate Khore child theme first if not created yet,please follow the following url.
Khore Theme How to activate a Child theme

2. Navigate through Appearance -> Editor , add following css in ss and save.

.video-card > div > div{
background:rgba(0, 0, 0, 0) none repeat scroll 0 0;
}

3. Save changes.