colon before lists
When a list may follow a colon.
Use a colon before a list only when an independent clause introduces it: Bring three tools: a saw, a clamp, and a level. Do not use a colon after include, are, or such as when those words already open the list.
Examples
UseThe kit held three tools: a saw, a clamp, and a level.
AvoidThe kit held: a saw, a clamp, and a level.