My mom had a appendectomy on monday & is the incision on her belly button is starting to look purple, like a bruise, is this normal?

Bruising normal: Some bruising is normal after any surgery -- the skin, underlying tissue, and muscle has to be penetrated, and that leads to blood vessel breakage (bruising) that heals on its own. Warning signs of infection on the incision site include worsening redness, swelling, worsening tenderness, pus. For these, she should be seen immediately.