Emperor Yellow/Green buildings

I've played a lot of Pharaoh back in the day, and a bit of Emperor too, but I never really got far in Emperor at all compared to Pharaoh. So now, i've came back to it to try and finish all the campaign missions, but I've been wondering, what does the Yellow/Green highlight before placing the building indicate anyways? Is that the Feng Shui bullshit that you need to check first? And what are the negatives of placing "Negative" Feng Shui buildings?