Red with a thumbs down means there's a message relating to the company being dangerous. Those messages show up with a red background at the top of the review page.
There's currently a flaw in the system with the Yellow hand. It's supposed to be only if there's a yellow background caution message, but also shows up of there's a blue background neutral information message.
I'm hoping to have the whole reviews front end overhauled this year. Searching needs some major upgrades.