As per http://www.kendoui.com/forums/dataviz/chart/scatter-chart-with-different-point-colors.aspx your ScatterLine really needs the ability to set the color of the lines between the points. It seems like an oversight that just needs to be fixed.
Hello,
You can use the series visual function:
https://docs.telerik.com/kendo-ui/api/javascript/dataviz/ui/chart/configuration/series.visual
Regards,
Alex Hajigeorgieva
Progress Telerik
This looks like a duplicate of http://kendoui-feedback.telerik.com/forums/127393-telerik-kendo-ui-feedback/suggestions/4045562-scatterline-color