When an area turns blue, very pale, or cold, it can mean that there has been a sudden change in the blood supply to the area. This can be serious.

There are other reasons for color and temperature changes. Bruises often look blue. A limb may turn blue or pale if you leave it in one position for too long, but its normal color returns after you move it. What you are looking for is a change in how the area looks (it turns blue or pale) and feels (it becomes cold to the touch), and this change does not go away.