- Contrast: Contrast refers to any difference of size, shape, or color used to distinguish text (or other elements, though here we’re focusing on text) from other pieces of text. The use of bold or italics is one common form of contrast — the difference in shape makes the bolded or italicized text stand out from the surrounding text. Increasing the size of headers and titles, or using ALL CAPS or smallcaps are other ways of distinguishing text. These techniques only work if used sparingly; a document typed in all capital letters has less contrast than one typed normally, so is harder, not easier, to read.
- Repetition: Repetition in your text is bad; repetition of your design elements is not only good but necessary. Once you’ve decided on a size and typeface for second-level headers, for instance, all second-level headers should look the same. For most documents, two or maybe three fonts — leaning heavily on one for all the body text, with the other two for headers and maybe sidebars — are enough. The same bullets should be used on every bulleted list. Information that appears on every page should appear in the same place on every page. Design elements — like horizontal rules between sections or corporate logos — should appear the same whenever they are used throughout the document. Repetition of design elements pulls the document together into a cohesive whole, and also improves readability as the reader comes to expect text that looks a certain way to indicate certain qualities (e.g. the start of a new section, a major point, or a piece of code.
The point of text is to pass along information. If you can’t read it, it’s useless. White and black contrast very well and that’s why most word processors use black text on a white background. Since just using black and white is boring, people like to mix in other colors. The key is that the background and the text need to contrast (be different) enough to be easily readable.
If you look at this post, you can see that each of the topics is in bold. That repeating element helps to make it easy to key in on the topics. Each type of heading should have the same styling. You should not change styles (size, font, color, etc.) arbitrarily. That means no thinking, “Well that last paragraph was green, so lets make this one blue and the next one red and..”