Grateful for your prompt reply. Will follow your advice later and let you know how I fare.
Yes, of course, I use photoshop and the version I have is CS5. I have done a couple of courses, particularly modules 1 and 2, and I have learnt a lot over the years, slowly and rather painfully, as I am a slow learner. However, there's always something new that crops up and that baffles me, like the present problem about changing the colour of a sea scene.
Many thks as ever, and kind regards.
GUZEPPI