@krassowski/theme-material/style/completer.css

Material theme for JupyterLab-LSP

.lsp-completer-theme-material .jp-Completer-icon svg {
  position: relative;
  top: 2px;
  left: 2px;
  width: 16px;
  height: 16px;
}

.lsp-completer-theme-material .jp-Completer-item.jp-mod-active svg path {
  fill: white;
}