Can I use red for buttons?
Red is a special color on buttons because it's used to signify a warning state. Buttons that have destructive actions for deleting data are red to warn users of potential danger. If your brand color is red, making your buttons the same color could conflict with any destructive actions on the interface.
Why is delete button red?
When designers use red for delete buttons, the color naturally gives users pause due to its connotations. Both deletion of a file or closing an account are good examples of using red in design.