In KitaBleu I have changed the background colour of nearly all boxes, left, right, middle etc.. but I cannot find how to change the background colour of the 'Shop by Categories' box. Can someone advise?

Is your goal to change the background of the whole box or just the title box?

To change the background of the whole box locate and edit the following lines in "skins\kitablue\styleSheets\layout.css"

Thank you Flashmount. In fact I did all that originally but there is still a problem as shown on the attached screenshot. When I insert the colour I want to change it to, there remains a white outline, which is not a border but the remains of the original white background. I widened the categories links and reduced the size of the white area, but cannot eliminate it completely.

Any ideas how I can eliminate the white and cover the whole box with the blue colour?

Do you have a link to the site? I can take a look at the code if you like!