Different color of my upper and lower parts of my teeth. (Photo)

Teeth are not one solid color. They are composed of multiple shades and textures. This is why restorations like crowns and veneers must take this into account or the restoration will look like a restoration rather than the tooth it restores.In your case, the discoloration at the base of your teeth is NOT part of your teeth but is clearly stain. This stain can be removed with a professional cleaning. I would also recommend a power brush to help prevent the staining from recurring. Regular visits to your dental hygienist can help prevent the stain from recurring.Good luck!

Teeth NATURALLY have gradients of color. Normally 3-4 shades. Professional cleanings will have zero effect. KoR whitening CAN

I appreciate your question, and I understand your concerns. Without an in-person exam, I'm limited in my ability to diagnose you. But here's some information that I generally give my patients with similar symptoms, that might help you make an informed decision on treatment. 
The “yellow” appearance of teeth near the gum line is due to a combination of staining and abfraction/abrasion of your teeth. Habits such as aggressive brushing (especially with hard bristled tooth brushed) can cause abrasions at the gum line. Abractions, on the other hand, are due to heavy biting forces such as from grinding/clenching or an improper bite. Both similarly create that yellow “notch” at the gum line, like the one that is present in your photos. The change in color is due to the underlying dentin layer of the tooth and the root becoming exposed. Annual cleanings will help with staining, but in most cases, a tooth-colored bonding or gum graft are necessary to correct the color and notch at the gum line. 
As I mentioned, an in-person exam with a dentist that has experienced with cases like these is always the best way to go. Best of luck!
Dr. Neil Hadaegh 
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