You can change the style of text (font, size, text face [e.g., bold, italic, underline], and color) within idea windows via the Text menu. There are individual sub-menus for modifying each of these text properties.
In addition, Idea Keeper allows you to define a default text style (via the Default Settings Sub-menu nested inside the Edit menu) and up to 10 style templates. Each of these style templates stores the style of text (font, size, text face [e.g., bold, italic, underline], and color) for quick formatting. The default text style is automatically applied to newly created ideas.
See the □ idea or look in the "Style Templates" submenu in the Text menu for a description of keyboard shortcuts for these features.