Welcome to healthcare Magic!
The bruises are made of blood in the local site.
It is normal for them to change color, because hemoglobin
gets denatured and mobilised.
Bruise is red initially then bluish then black then yellowish pink and lastly vanishes after about 21day in toto.
You do not need worry, just forget seeing it and it will be okay by itself.
Wish you a great health!