ETA: Now I know the value of getting a precise question :-) Thanks for all your help. What I was looking for was the colour like Teal (but obviously not Teal - have you ever seen a Teal they're not the colour called Teal either). I was asking because I had a very shiny dress in the eighties which was this petrol blue colour and I wanted to use it in a story with a US setting. But now I know petrol in the US isn't the same colour as ours and the name I'm looking for is in the Teal range of colour charts - I'm off to look at US fabric sites.
Thanks again - this community is great.