I bought the Launcher template and deleted all elements from a page. The body element seems to be inheriting this midnight blue swatch as a background color from -somewhere-. I can’t find where this is being set and if I try to change the color to something else, Webflow will give it another class (Body 2).
The color is being inherited from the Body html tag. Select Body in the Navigator panel then go to the styles panel. In the dropdown selector of the class input box, choose the Body tag. Then you can go down and remove or adjust any default styles.