captain scarlet and the mysterons

[seiko123]

who said= we are the mysterons

[SurreyGuy]

As I recall, that specific dialogue was never said/heard.

One assumes that the dialogue "this is the voice of the mysterons. we know that you can here us earth men (and so on and so on)" was spoken by Captain Black

[sddsddean]

If you mean which actor said it, it was 'performed' by Donald Gray who also did the voice of Colonal White. Capt Black was actually just the Mysteron agent and there is no reference to the 'voice' being his. Indeed, in the very first episode Captain Black is still a Spectrum agent when he attacks the Mysterons Mars base and you hear the voice for the first time before Capt Black is mysteronised.