Can anybody tell me what colour the standard head should be on a 2011 st290? mine is grey but as you look closely you can see black under it? just from bottom of head from where it sits on the cylinder?? It worries me because the previous owner tells me he used to take the head off to check the barrel for scores and scratches??

It should be grey, If the bike runs ok don't get paranoid about it. If It has problems it could be that its been siliconed up instead of fitting new o rings, It could be the black you are describing at the joint!