Standing for long hours through out life has its own complications.
You may be suffering from varicose veins
. Here the veins may become prominent and visible.
The torturous course of the vein is due to bulging of the blood vessel.
So blood vessel wall may become weak, this weak blood vessel will burst on its own or in the event of slightest injury
which normally doesnt cause any bruise
Reason for this condition is the blood from legs is harder to get to the heart. So most common location of varicose vein is legs.
Regarding treatment, increase your time sitting , raised legs while resting.
You need to consult your surgeon for further assessment to evaluate the extent of bruises.