I have tried with the following:
.kn-table-group.kn-group-level-1 {
background-color: #195E93 !important;
color: #FFFFFF;
font-weight: normal !important;
}
Try the above css. I have removed the !important as this should be used sparingly. I have also made the target more specific by adding .kn-content and I have add the td so you are targeting the element that has the text, also making it more specific.
In the above images you can see that specificity on first image has that extra 1 making it more specific.