What is the difference between dark and light skin ?
— Dark and light skin is a important option in the theme options.
Light skin is used on light background image.
Dark skin is used on a dark background image. You can specify the text skin in the style tap of the column settings in the header content block.
As a result, the light skin will make your primary menu font color black and sets the logo to the one you have chosen in theme options navbar -> logo -> logo light. The same applies in the opposite way for the dark skin.