Hi Patrick.

Yes, the standard Kirby colour was an orange-red.

Unleaded and leaded.
My understanding is that it is simply not an issue for these small engines.
There is no shortage of debate on fuel in these forums though.

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=17050

Quote
It was not a nice engine to operate in my experience, but they were quite durable mechanically.
Thousands would disagree - including myself.
They made over 1/2 million Kirby engines here.
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=66618

Cheers
-------------------
Jack