I would be painting anyway between tenants and wouldn't have charged you, unless you had put up murals or painted a very strong color that needed primer and several coats.

And you try some circumvention, it's not just clueless home owners your dealing with, it's a savvy investor who is very skilled at the angels, and how to crush someone coloring outside the lines. 

Most homebuyers walk into a home with broken weird color blinds, gross dark burgundy and mustard paint and an old icky pink carpet and can't imagine the potential.

Paint color depends on style of house. 

Someone scrawling all over the accent wall you put up so many color swatches for to find the right paint?

@Karim Wahba, to add a little color to Chris's comment: the typical syndication costs between 10 and 15k to setup.  

Most of them are $10 or a bit more with extra digital items included, and it's very easy to add your info, brand the colors and then upload it to Dropbox.

2) How important is it to have a variety of colors throughout the home?

Painting houses a neutral color is the easiest and least expensive way to get houses rented or sold. 

Or keep the uppers and lowers the same and contrast the island color.