It is very common for me to get e-mails asking what a sender meant by having only certain text in their e-mail purposely changed to red.
Red is an aggressive color. The term “seeing red” means that someone is mad or so upset that they are seeing red. So it goes without saying that when it comes to communicating with the written word it is safe to assume when someone changes select text to red — that they are making a point.
If in a business letter if you changed only certain words or sentences to red, what would that mean? It would mean you are making a strong point. It would mean you are adding a robust emphasis to those particular terms or sentences. Same goes for e-mail.
And, when you use red, you leave the level of emphasis up to the person on the other side to decide the level of emphasis you may have meant. Plan on them adding more emphasis than you may have intended!
Use our wonderful vocabulary to communicate what you mean, your anger or your emphasis instead of relying on formatting to get your message across. Turning selected text into red is the easy way out and risky at best.