[GnL]

Not to be too technical here, but blood is not used for color, it is used as a fining agent, to soften tannins in red wines (to reduce astringency). In the U.S., we often use egg whites or gelatin for the same purpose.

[Happygal]

I watched a programme here in Ireland this week, made in a French wine vineyard.
In that, they too used egg whites to remove tannins etc.

[texasflower]

That is completely disgusting.

[Bob J]

Fining is used to remove suspended particulates. In other words, clarify the wine.

[Harmless Teddy Bear]

Not to be too technical here, but blood is not used for color, it is used as a fining agent, to soften tannins in red wines (to reduce astringency). In the U.S., we often use egg whites or gelatin for the same purpose.

Doesn't exactly matter why they use it but it does mean french wines are not Kosher. Another good reason not to drink them.