Flow/browser/vue-flow/src/assets/lines-theme.css

.lines {
  --header-background: #fff;
  --header-color: #333;
  --background: #fff;
  --background-transparent: rgba(255, 255, 255, 0.9);
  --background-secondary: #fff;
  --background-tertiary: #fff;
  --normal: #333;
  --normal-secondary: #999;
  --primary: #0be;
  --primary-darker: #0ae;
  --primary-lighter: #6080b0;
  --primary-inverse: #fff;
  --secondary: #666;
  --secondary-inverse: #fff;
  --node-label: #fff;
  --node-socket: #444;
  --node-socket--withvalue: #44f;
  --link-hover: #f00;
  --selector-background: rgba(0, 0, 200, 0.1);
  --selector-color: var(--primary);

  /*--transition-speed: 0.3s;*/

  /*--transition-speed-slow: 0.7s;*/
}

.lines .app-header {
  box-shadow: none;
  border-bottom: solid 1px var(--border-color);
}

.lines .split .splitter {
  flex-basis: 1px !important;
}

.lines .split.resizeable.horizontal .splitter::after {
  background: transparent !important;
}

.lines input {
  border: solid 1px var(--border-color);
  box-shadow: none; /*0 1px 3px rgba(0, 0, 0, 0.12), 0 1px 2px rgba(0, 0, 0, 0.24);*/
  color: #777;
}

/* chat */
.lines .flow-chat__container input.handle {
  background: var(--background);
  color: var(--normal);
  box-shadow: none;
  border-bottom: solid 1px var(--border-color);
}

.lines .flow-funcs__src {
  background: transparent !important;
  border: solid 1px var(--border-color);
  text-shadow: none;
  color: var(--normal);
}

.lines .flow-funcs__src b {
  font-size: 1.2em;
  text-shadow: none;
  color: var(--primary);
}

/* left panel */
.lines .hx-collapsible {
  border-bottom: solid 1px var(--border-color);
}

.lines .hx-collapsible__header {
  height: 50px;
}

.lines .flow-node__body {
  fill: transparent;
  stroke-width: 3px;
}

.lines .flow-node__label {
  fill: black;
}

.lines .flow-node--selected .flow-node__label {
  fill: white !important;
}

.lines .flow-panel__selector {
  flex-basis: 51px;
  border-bottom: 1px solid var(--border-color) !important;
}

.lines .flow-panel__selector .active {
  color: var(--normal);
  background: transparent;
  position: relative;
}

.lines .flow-panel__selector .active::before {
  content: " ";
  position: absolute;
  bottom: 0;
  height: 3px;
  left: 0;
  right: 0;
  background: var(--primary);
}

.lines .flow-main h1,
.lines .flow-main h2,
.lines .flow-main h3,
.lines .flow-main h4 {
  color: #222 !important;
}