It can be a yellow flag for me if a would be tenant wants to immediately paint my white walls (that I have usually just painted my go to white).

Those yellow walls are actually white!

Never use yellow for the type color.

WHAT is that third picture with the green and yellow circles?!?

As far as the persistence part, I'd send them a yellow-letter or postcard every 90 days or so, reminding them that they could call you at any moment and take the 'problem' off their hands.

If you are doing yellow letters you send them a letter to their address, but the main thing is you don't have much time because most will be auctions in about 6 weeks or less.What I say is, "You may have already taken care of this but you home is on the foreclosure list and what wondering your plan?"

TemplateI downloaded a notebook paper template to do my own yellow letters.

Should I send a post card or yellow letter directly to the owner?

I use incandescent to get a warm glow, LED in kitchens and garages, clear bulbs to get sparkle and use the old style yellow filament bulbs to highlight a great light fixture.  

Hard to get reliable data from zillow,  numerous examples of houses we sold that, yellow dots show what we purchased it for, not sold, seriously messes up comps.