Idk honestly, this one might be quite a bit more annoying than other scenarios but I’m a noob and always do 60 units + like 8 trebs and it worked for me in this scenario too (on hard)
A Castle in front of your base asap, iirc Green sends SO so focus them with the Castle, steamroll Purple with the 60 units (prob either e.Tarkan or Paladin + CA)+ trebs. Purple wont surrend bc that rat rebuilds in Orange base but after cleaning his initial base just clean Red in north then Green in south and then Orange + Purple, it will take longer than many scenarios bc Purple rat dont want to surrend but I don’t recall having any more complications, really