A colon before a list

[herbivorie]

I have seen a style guide that says we should use a colon before a list.

For example,

The roles of the manager include the following:
1. Implement risk management and loss control policies.
2. Maintain and actively promote a safe and healthful working environment.
3. Take prompt, appropriate action to correct unsafe conditions.

Is a colon like the above one always necessary in English, or does it depends on the style guide?
I mean, is it grammatically okay if I use a period instead of a colon when I don't have to follow a style guide?

 

[Raymott]

I always use a colon. That makes it obvious that you're introducing a list. For example your list might be set out linearly, as below.
"The roles of the manager include the following: Implement risk management and loss control policies, maintain and actively promote a safe and healthful working environment ..."
In this case a period is wrong.

 

[Barb_D]

Some styles may allow you to omit the end punctuation before a bulleted or numbered list. You need it in running text, as shown above. Using a period in either format would be wrong.

 

[Tdol]

"The roles of the manager include the following: Implement risk management and loss control policies, maintain and actively promote a safe and healthful working environment ..."

I'd use a colon too, but I wouldn't use an upper case letter after it.

 

[Raymott]

I'd use a colon too, but I wouldn't use an upper case letter after it.

Nor would I usually. I copied that and forgot to change it.