1971 340 engine color blue?

I have a late build 1971 Duster that the 340 engine is blue in color.
Can anyone explain when and why Ma Mopar changed this during 1971 model year cars?

the 1971 model year continued with 340 engines being assembled at the Windsor, Ontario engine assembly plant & will be stamped GW340 on the pad on the front of the block below the driver's side head. These engines are painted "street HEMI orange".

G = 1971
W = Windsor
340 = cu.in.

winter of 1971 the 340 engine assembly was moved to the Mound Rd. engine assembly plant in Detroit. These engines are stamped GM340 and are painted "Chrysler Corporate Blue".

G = 1971
M = Mound Rd.
340 = cu.in.

there were 5 car assembly plants (A,B,E,G,R) & 3 body styles (A,B,E) plus automatic VS. manual transmission (and A/C spec engines) that used the 340 for the 1971 model year, so the transition dates between the use of Windsor VS. Mound Rd. engines varies.

from allpar:

GREAT Info ...... THANKS

Here's what to look for on your block

AGAIN ... Great info THANKS