Babylon.js/inspector/sass/_tree.scss

// Color for a property type
.property-type {
  color:$color-bot;
}

.property-name {
  color:$color-top;
}

.insp-tree {
  overflow-y: auto;
  overflow-x: hidden;
  height    : calc(50% - #{$tabbar-height} - #{$searchbar-height});
  
    
    .line {
        padding:3px;
        cursor:pointer;
        // Hover
        &:hover {
            background-color:$background-lighter;
        }
        // Line active (selected)
        &.active {
            background-color:$background-lighter3;
            .line-content {
                background-color:$background;
            }
        }
        // > before title names
        &.unfolded:before{            
            width      : 1em;
            height     : 1em;
            line-height: 1em;
            display    : inline-block;
            font-family: 'FontAwesome', sans-serif;
            content    : "\f078";
        }
        &.folded:before{            
            width      : 1em;
            height     : 1em;
            line-height: 1em;
            display    : inline-block;
            font-family: 'FontAwesome', sans-serif;
            content    : "\f054";
        }

        // Sub lines
        .line-content {
            padding-left:15px;
            &:hover { 
                background-color:$background;
            }
            .line:hover:first-child {            
                background-color:$background-lighter2;
            }
            
        }
    }
}