I thought I'd chime in here for some clarification. Joe Frazer points out
Many years ago a non-KF vendor was marketing the light green paint as correct for the 51-53 engines
That vendor was Hirsch and they touted it as correct for all KF engines, and as Joe points out, it is not. It would be correct for the 1949/50 cars only and some argue the 1951 Frazer (if anyone knows for sure, chime in).
The '47/'48 cars had gray engines, the '49/'50 had the light green, '51-'53 were the green that's been discussed on here and that Dave posted the info on (thanks by the way!) The '54-'55 Kaisers had a dark maroon on the engine.
I believe Hirsch is still selling the light green as "KF" green so beware. There was pretty nice Henry J four cylinder for sale recently which certainly had the Hirsch paint on it.