Use a colon:

• after a clause that formally introduces a passage.

The architecture consisted of a wide variety of styles: homes with collonades, Italian villas surrounded by formal gardens, and Californian ranches.

• to indicate that what follows is either an example, or elaboration of what has just been written.

City-county consolidation is more than a term: it means the process of merging a county government with all municipalities.

Either a capital or a small letter may be used following the colon. When the material following is a complete sentence, a capital is used. When the matter is a subordinate element, a small letter is used. If, however, the colon is used in a title, the first word following the colon is always capital­ized.

Perceptual Conditions of Association: a possible confusion