mermaid/src/less/forest/sequenceDiagram.less

.actor {
  stroke: @actorBorder;
  fill: @actorBkg;
}
text.actor {
  fill:@actorTextColor;
  stroke:none;
}

.actor-line {
  stroke:@actorLineColor;
}

.messageLine0 {
  stroke-width:1.5;
  stroke-dasharray: "2 2";
  marker-end:"url(#arrowhead)";
  stroke:@signalColor;
}

.messageLine1 {
  stroke-width:1.5;
  stroke-dasharray: "2 2";
  stroke:@signalColor;
}

#arrowhead {
  fill:@signalColor;
}
#crosshead path {
  fill:@signalColor !important;
  stroke: @signalColor !important;

}
.messageText {
  fill:@signalTextColor;
  stroke:none;
}

.labelBox {
  stroke: @labelBoxBorderColor;
  fill: @labelBoxBkgColor;
}

.labelText {
  fill:@labelTextColor;
  stroke:none;
}

.loopText {
  fill:@labelTextColor;
  stroke:none;
}

.loopLine {
  stroke-width:2;
  stroke-dasharray: "2 2";
  marker-end:"url(#arrowhead)";
  stroke: @labelBoxBorderColor;
}

.note {
  //stroke: #decc93;
  stroke: @noteBorderColor;
  fill: @noteBkgColor;
}

.noteText {
  fill:black;
  stroke:none;
  font-family: 'trebuchet ms', verdana, arial;
  font-size:14px;
}