.ag-header-row-column{
    background-color: #34495e;
    color: #cecece !important;
}

.ag-header-row-column-group{
    font-size: 15px;
    color: #cecece !important;
}

.ag-header-viewport{
    background-color: #34495e !important;
    color: #cecece !important;
}