I can't speak about shoulder replacement specifically, but 2 weeks after major ortho surgery is very early days and swelling is to be expected. Yours looks a lot like my hand looked last year for 6-8 weeks after a simple thumb surgery.

You may be able to reduce it some by icing for 20-30 minutes several times a day. Both shoulder and swollen area. Gently massaging the swollen hand and forearm with a stripping motion up the arm can also help move the fluid back toward the trunk of your body where it can be eliminated.

As for the "electric charges" your nerves are letting you know they are irritated and angry. Many were disturbed in the surgery. You will experience these and a number of other sensations over the next weeks and months as they (very slowly) heal and regenerate. They may tingle, feel hot or cold, feel like electric shocks, maybe even feel like something is crawling on you, or water is dripping...

The dark color you see is blood that has accumulated in the tissue from the operation, eventually you may turn several colors before it goes back to normal.

Time, ice and therapy are the great healers! Good luck, and be patient - this was major surgery, and your body needs time.

(Easy for me to say, huh? I haven't had surgery this summer - but I did it twice last year...
Sue