[napy8gen]

1. The category name cannot center easily because it is inside a colspan column. It can be centered using a CSS overwrites.

paste this inside style manager> style name> edit templates> CSS Templates> css_additional.css

.forum-list-container .category-header .category{
    width: 100%;
    text-align: center;
    display: block;
}

2. Category background color can be different using CSS overwrites but there is no stylevars yet for this.

you have to find the forum category id whether from browser inspect or from forum manager.
for example

.forum-list-container .category-header#forum18{background:#000;}
.forum-list-container .category-header#forum18 .category{color:#fff}

This will make the category header black, the category text white.
paste this inside style manager> style name> edit templates> CSS Templates> css_additional.css