The following properties are used to set scrollbar colours, in this example for the document body.

body {
  scrollbar-face-color: #DEE3E7;
  scrollbar-highlight-color: #FFFFFF;
  scrollbar-shadow-color: #DEE3E7;
  scrollbar-3dlight-color: #D1D7DC;
  scrollbar-arrow-color:  #006699;
  scrollbar-track-color: #EFEFEF;
  scrollbar-darkshadow-color: #98AAB1;
}