Jetcat engines were first imported to the US int 1997-98 by Golden West models (the same Golden West who built and sold the FD3-67 engine). The engines that were imported by Golden West all had blue covers, I think they went to the purple covers after Jetcat-USA was formed.
I had serial #0017 P-80 that I bought from GW, and it had a blue cover. It finally had to be retired around 2005, but I kept my blue cover for the P-80 that replaced it.