Thick flange Cooper S block

[e-type]

Have just taken an S block apart, it looks like it´s painted blue from new, I have seen this before.
I have heard them being called "blue blocks"
But they where never blue in the cars?
Any info on this?

[Spider]

I don't have much at all to offer, except to say that I also have one here, it is a very very late S Block.

[spoon.450]

I also have a very late ( mk 3 ) S engine that appears to have been blue from new. I bought it a couple of years ago from Nev who I think got it from the USA ??

[mk1]

The blue paint was applied after casting & cleaning but before machining of various engine components. Red oxide was most common, but so were blue & yellow amongst others.

I don't think there was any significance to the colour used.