Also, you can create a formula rich text and use the follow code:
if(isnull([Design Start Date]),"<CENTER><div style=\"color:white; background-color:blue;\">"& " blue" &"</div></CENTER>","<CENTER><div style=\"color:white; background-color:green;\">"& "Other Color" &"</div></CENTER>")
Or, simply you can use Color-Coding option in the report settings. All is up to you.