First create a Waterfall plot. Then right click on one of the traces and select Plot Details from the context menu. The Plot Details dialog box should appear and the Group tab should be selected. UNcheck 'Line Color.' This property will no longer increment and line color will all default to black. Select OK, then in Origin choose File:Save Template As... and save as the default template name WATERFAL.OTP.
Lorraine, thanks for the quick response. Unfortunately, it does not appear to be quite adequate. When I do as you indicate, no Group tab appears. (I am trying a version 6.1 demo down loaded some months ago.) Thanks.