This document explains how the ticket number coloring can be done based on the SLA.
In Service Desk Options Manager there is the option "TTV_Highlight" under "Time-to-Violation".
When you have a Service Type event configured to set "CR SLA Violation=Predicted" with a Delay Time of "3hr in 4hr resolution (refer to the "out of box" 4hr resolution Service Type Detail - 4hr warning), the request will turn yellow if the event condition is true at 75%. The delay time can change to 2hr (50%) or 3hr 30 mins (87.5%). It means the warning time can adjust to different value.