While the color do not differentiate the types of bullets, I do believe they signify types of rims and powders. Those with red varnishes tend to have a different rim making them harder to load on the rifles not "N" stamped, (wrong info deleted). Sort of helps the shooter be aware of them if they haven't noticed the absence of the "N" stamp on their rifle.
Here is a link (in French) showing the different types of balles
, their weights and types of powders - with pics:
The story goes that Oscar killed a "sniper" who was up in a tree,,,
He told the story that it was a French woman shooting at US troops.
If I had a dime every time I read this on various forums, I'd have a sizeable sum of money by now. I'm sure it's false. Too many people out there looking for French-bashing stories including tales of French women in the trees by the thousands taking pot-shot at GIs.