Change the overall appearance of a notebook by editing the styles in its stylesheet.
Open a notebook’s stylesheet for editing
You can customize individual styles in a notebook’s stylesheet.
To change a style in the current notebook, choose Format ▶ Edit Stylesheet:
Choose a style to modify
In the stylesheet that opens, choose the style you want to modify:
Adjust the style
With the style cell selected, use the menus to adjust its style—for example, changing the color of the text:
All cells with that style in the current notebook change accordingly: