@Walter Lee Bandy Jr I bought my 1st investment property in 2015 and had this same question. I scoured and scoured the web looking for at that time. I now have 8 doors. The colors I settled on and the advise I received seems to be working wonderful for me. There hasn't been a single person not impressed with how well my units have turned out.
Advice I have followed:
Paint all of your units, all rooms in every unit, the same color on the interior. You will always have extra touch up paint on hand if needed between tenants. You never have to worry about matching and it will always be interchangeable between any rental you havle.
Save effort, paint, and money by painting the ceiling with white primer. No paint. I usually do 2 coats of Sherwin Williams Pro Block. Close equivalent to latex kiltz. It covers well, seals, and is a very flat finish.
Primer on the wall I use Sherwin Williams Pro Block and have them tint it (for free) so it is very close to my wall paint color.
The wall color I consistently came across while researching was Sherwin Williams Navajo White so that's what I settled on. Don't let the name fool you. It's not white. More of a light tan. Every potential tenant that looks at my places LOVE it.
For all trim I use Sherwin Williams Pure White. It is a base color that doesn't need to be tinted so you can pick it up and be ready to go at any time. It makes the contrast between wall and trim really look clean! On a couple of my recent rentals I decided to step out of the norm and paint my interior doors black. I had a lot of people tell me NO NO NO!!! LOL But I experimented anyway and it gave my apartments a ver modern appeal. They were believes after that! When paired with black and stainless appliances it looks spectacular! If I knew how to post pics on her I would. You'll notice I used all Sherwin Williams. I have no affiliation with them. I just know its quality paint & I liked the fact they keep all of my color & rental information in the computer. Plus I could call ahead any time to have them mix up what I needed. Also being a landlord I was able to receive quite a discount. You have to ask them about it though.
I hope this helps. Good luck.