By Dr. Mercola. Any type of traumatic injury, such as a fall, can cause capillaries (small blood vessels) near your skin's surface to break and leak red blood cells. This causes the reddish-purple or black and blue appearance of bruises on your skin.
In Act III, Scene I we learn that Macbeth has hired murderers to kill Banquo and his son. Macbeth does this because he realizes that Banquo poses a threat to Macbeth's rise in power. At the same time, Banquo loses trust in Macbeth but decides to fake his loyalty for safety.He also wonders if the witches' prophesy concerning his sons will actually come true, which puts them directly at odds with Macbeth.Banquo is murdered in Act III, Scene III. However Banquo's son escapes.When the murderers tell Macbeth that the plan was not completely successful Macbeth realizes that Fleance still is a threat but is happy that no other children will be born of Banquo.t the same time, Banquo loses trust in Macbeth but decides to fake his loyalty for safety. He also wonders if the witches' prophesy concerning his sons will actually come true, which puts them directly at odds with Macbeth. Banquo is murdered in Act III, Scene III.
What warning does Banquo give Macbeth? Banquo warns Macbeth that he should not be tricked by the  prediction of the three witches. Banquo's warning is in Act 1,  Scene 3, lines 123-4 of the play 'Macbeth'.