What symbol does the protagonist use to send text messages when writing novels?

It is obvious to use double quotation marks to distinguish speakers, which is convenient for readers to distinguish subjects quickly.

For example, Xiaoming sends a message to Xiaohong: "Have you eaten?" Will it be abrupt to see the article?

And the usage of this symbol. In many texts, most of them are available.

For the question of commas and colons, use commas in sentences and colons in direct speech, which means that words are followed by colons. If there are only words in a sentence, you cannot use colons. This is a basic punctuation application.