lists and commas

[hatwoman]

should there be a comma after the second to last thing in a list, before the and? I say no. dh says yes.

blue, green and red
or

blue, green, and red

I don't actually mind the latter and can see it might be used to make you read something slightly differently, but I'm sure I was taught the former at school.

Blue, green and red.

Agrees with specific.

You can do either. In the second example, the final comma is what we know as an "Oxford comma". But the less punctuation, the better.