color dot markings

[Andy Goodell]

does anyone know what red and yellow dots on houses mean? i have been watching a property down the street from me, a duplex that has been vacant for some time now, i did some research and got a hold of the deceased owners girlfriend and she said that the bank had already taken possession. This one has a yellow dot that looks to be maybe a little bigger than a half dollar on the front porch pillar. i have seen this on other properties as well, one boarded up with the same yellow but also a red one next to it. wondering if it is city or bank markings. . .? any info would be great as i couldn't find anything in my web searches