normally carried out when cold - coz otherwise temp cannot be maintained unless yu have the engine running - and if yu have ever tried adjusting tappets with the engine running - yu will know wot i mean!
I used to set the tappets on my Triumph with the engine hot. I would set them so they just gripped a fag paper and it ran as sweet as a nut, Can't remember wether they were red or green now but definitely weren't liquorice.