I would offer a color pallet for the tenant to choose from. 

Something that helps me is I have a provision in my lease that describes the paint brand, texture, and color of every room for future reference.

Even if you have to offer a small tenant concession, it's worth it.Speaking of concessions - I offer something small [like a ceiling fan or one room of custom color paint] for them to sign another term once the current lease is about to expire.Also, I assume/hope you have a rock solid lease.  

New properties tend to sell at a slight premium to 10 year old buildings, but that's because everything is new, you get to pick colors and finishes to customize it to your taste. 

Here is the Seattle definition: “Discrimination” means any conduct, whether by single act or as part of a practice, the effect of which is to adversely affect or differentiate between or among individuals or groups of individuals, because of race, color, creed, religion, ancestry, national origin, age, sex, marital status, parental status, sexual orientation, gender identity, political ideology, honorably discharged veteran or military status, alternative source of income, participation in a Section 8 or other subsidy program, the presence of any disability, or the use of a service animal by a disabled person.

I couldn't stand having others involved in my investments, who could tell me what color I could paint it, or tell me I had to pay for garage doors, on and on.It would be good if you could sell it, as Greg S mentioned.  

I see where that also probably colors your perspective.

Because a tenant tells you so, that doesn't mean they are being petty or making things up.Now, if she was saying she didn't like the color of the floor tiles - that would be a very easy "no."  

if its late on the 2nd, I call or text, if they dont have it or dont have a plan, they get a 5 Day that day, I suggest Printing your 5 Day on Bright colored Paper in Bold Print, Tape it to the front door, so it can be seen from the street.

Replace the furnace filter and look at the color... a non-smoker apartment filter will look grey, a smoker apartment filter will be yellowed. 2.