how to give color to a wordpress tab using tabby responsive tabs plugin

I am using tabby responsive tabs plugin to make this tabs but I want when the page load the first tab get orange color and when I click on another tab the color change with my code now it just gives color when I click on it

.responsive-tabs__heading,
.responsive-tabs__list__item {
    font-weight: bold!important;
    color: black!important;
    background-color: #E8E8E8!important;
}

.responsive-tabs__heading:focus,
.responsive-tabs__list__item:focus {
    background-color: #ff6720!important;
}

Based on your live example I noticed they add an active class to the active tab:
.responsive-tabs__list__item--active

.responsive-tabs__list__item.responsive-tabs__list__item--active {
background-color: red!important;
}

Let me know if this worked for you.