Thanks for the help and welcomes everyone. Thanks especially for the signpost to the tutorials! its been really hard to find info on PSP on the web so have been struggling a bit. in the end I managed to change colour using the selection tool and paint brush - I could not get anything else to work really so I must be missing somerthing basic or not have one of my settings right. think I need a couple of hours to play around with it and experiment a bit more!
Anyway, thanks again and no doubt I'll be back with more Qs!