Hi Liam,
The white background was to show that the aircraft belonged to a neutral country, i.e. Ireland.
I'm not to good with my history of Irish flags but here goes, I'm open to correction on this one:
The green is for the Catholic tradition, the orange is for the protestant tradition, and the white is for peace between the two traditions.
Like I said, correct me on the flag if I'm wrong.
Regards,
Frank.