The hair follicle is an indentation in the skin, inserting a probe/needle into it is like placing a straw into a beaverage bottle, as long as you don’t break the sides or puncture through the bottom, you have no problems.
A good electrologist will be able to provide you with trouble free skin with little or no discoloration, and any discoloration experienced would be temporary. The overwhelming majority of my clients experience nothing more than some short term redness and and maybe some temporary swelling, based on how much hair removal we do in any particular area.