My opinion is that there are two possible cases.
- Bullets may be used as part of a sentence or paragraph, in which case regular capitalization and grammar rules apples.
- Bullets may be used as a sort of Graphic Communication (eg. in a Presentation) - in which case anything goes
For example, under case one, I might list
- an apple,
- a banana, and
- a grapefruit.
In this case, I am interjecting bullets into my sentence, but the sentence should remain readable. This becomes more useful with complex lists, which may refer to
In this case, the above list is in fact a grammatical sentence, but the bulleting makes it easier to read, and as such the capitalization should maintain it's regular sentence-based form.
However, if I want to do something graphical in a document, or for a presentation, I say anything goes which effectively communicates. I might do this:
- NO: Red, Green, Yellow
- INCL. NO: Apples, Bananas, Grapefruits
- Legumes (Except on the 30th of the Month)