Tony -
You really picked the "MOTHER" of all color questions to come out of WW2.
I have my own ideas about this, but rather than take up all the space available on this forum, please do the following:
Go to the IPMS Stockholm web site.
Click on HELPDESK - REFERENCE.
Then click on PHOTO COLLECTIONS.
Then click on WORLD WAR II COLORS - IN COLOR.
There are two extensive articles on this subject, A Story About Lou IV and Seeing Is Believing: Lou IV Addendum. These articles give just about all of the possible arguments for and against both the blue and green. Some of these arguments can get a little technical, but these are best articles that I've seen on the subject.
When you are finished reading these, please tell me. Was it blue or green? What blue? or What green?
Or both![:0]
Pete