The nipple on one side has changed color no bleeding no tenderness no hardness noted I am a nurse never heard of this is it a problem

Is it a problem? I don't THINK it is a problem. I haven't heard of it before. It is something that I would talk to a doctor about. It could be a hormone problem, but those hormones should be long out of your system by the age of 78.

Talk to your doctor about it to make sure it isn't a problem you should investigate more.

A very remote condition to look into is Paget's Disease (of the nipple, not bone) although darker skin is not a typical symptom.
I wonder if you have blocked sebaceous glands there.
I'm totally guessing!

Speaking as someone with all sorts of weird skin changes over my 70 years, including discolorations that come and go, as well as basal cell, I think I would go see a dermatologist.

Speaking as a breast cancer survivor, any time you have changes in your breast, it should be examined by a doctor.