I was just asked about the potential SEO problem on a redesigned site that has a large background image and uses black font. The concern is that there is also a background color set which black. The background color is set for the area below the background image. So the question is whether Google (and the others) will be able to interpret that the black font text appears with an image background and is not black font on black background?
Ten years ago, the SEO shortcut was to keyword stuff white font on white background so I would agree "usually" would have applied when Google had noticed the trend. I am thinking and hoping that they would sense that the questionable text was placed over the background image. The sites have a lot of other things going for them SEO-wise including age, low bounce rate, etc so that could offset the potential flags.
i do not agree with the fact that Google will "see it." if you are using an image as your background, how in the world google will know which color the image is? image has a name like background.gif or bg.gif or whatever. its not html color code that google will corelate with the text color. if you are using html color code for your background rather than image, then google will know it for sure Even if google cannot see through this trick, there is no need to hide text on your site actually. if you are hiding text, then most likely it would be for keyword stuffing which will not get you anywhere. if you are using legit content, then there is no reason to hide. you can just add them on your site making it visible. if your site layout dones't allow you to add or display text on the main page, then put them at the bottom of your page. even if you cannot add the texts anywhere on the front page, add them on inner page and use a sitemap. what i'm trying to get at is that there is no valid reason for which someone would want to use hidden text
easy - google can check image and see what color the background is and how close it is to the text color. after it sees it, it will be passed to manual check to someone from google team. of course google cannot say for 100% you are cheater but it can guess you are and then make you on list to be checked manually. and then it's end of story for your site i strongly don't see the reason to cheat in such way. absolutely no sense. why not just make things as they should be?
If your hex is close, you are flagged, I noticed it in my webmaster tools>html suggestions. It has since been changed. Not trying to keyword stuff, just was curious. We'll be changing to a image based background soon.