What color is best for delete button?
Used correctly, it can prevent the user from doing something dangerous which cannot be reverted. 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.
What are danger buttons?
"Dangerous" buttons are buttons that users should never click by accident. Typically these are secondary action buttons that cause destructive actions, regardless of whether they require confirmation or are undoable.