I deeply apologize for bumping such an old thread, but I just noticed I never said thank you for the color suggestions, nor did I answer Sinners last question.
After a bit of hybernation I am slowly getting back to building, now that my kids are becoming old enough to play with Lego. So I will get back to some abandoned projects and I will build this cannon here as a stationary one. So I´ll go with orange, as Sinner suggested.
Oh, and yes. I take this opportunity to announce that I am officially back to Eurobricks as your good old Topic Killer :D