Stir the sugar, lemon juice and water in a pan and bring the liquid to the boil. Simmer gently until it thickens and coats the back of the spoon. (If using food colouring, add it at this stage.) Stir in the rose-water and simmer for a further 2-3 minutes. Leave the syrup to cool in the pan. Pour into a jar or bottle and seal tightly. Store in a cool place and, once opened, in the refrigerator.
Dilute 1tablespoon per person with cold water, and serve chilled, with ice.