What kind of a Review is it?

I have finished James' The Ambassadors and am taking notes and basking in its excellencies. Here is my beloved Lambert Strether, describing how he bides his time in Woollett, Mass., and the extent to which he keeps away from the business which makes Mrs. Newsome and her son Chad so very, very rich. His friend Maria asks if he is involved in the business itself:

‘Oh no, I don’t touch the business.’

‘Only everything else?’

‘Well, yes—some things.’

‘As for instance--?’

Strether obligingly thought. ‘Well, the Review.’

‘The Review?—you have a Review?’

‘Certainly Woollett has a Review—which Mrs. Newsome, for the most part, magnificently pays for and which I, not at all magnificently, edit. My name’s on the cover,’ Strether pursued, ‘and I’m really rather disappointed and hurt that you seem never to have heard of it.’

She neglected for a moment this grievance. ‘And what kind of a Review is it?’

His serenity was now completely restored. ‘Well, it’s green.’

‘Do you mean in political colour as they say here—in thought?’

‘No; I mean the cover’s green—of the most lovely shade.’ 

My favorite is how his "serenity" is "restored" when he can return to the solid ground of describing how pretty his little magazine is.