I think the RPSI site means red plates with brass letters. All SLNC locos had black plates with red letters/outlining , unless recently outshopped at Dundalk, where the staff seem to have preferred some bling. Manorhamilton generally quickly rectified this.
Erne is basically in Barry condition, sadly. Totally agree re Downpatrick but she requires so much money spent v the money she might generate that I fear we will never see her steam. It’s especially depressing given that she was less than 25 years old when her last fire was dropped.