An idea is colour schemes. They have been proven to get their message across better because they stand out (and look pretty). If you are using binary values then I would say do something similar to what [Benny Skogberg has proposed](https://ux.stackexchange.com/a/34173/3865) but with colour. Then comes the decision, Red for no and Green for yes? Red for hot and Light blue for cold? Just find a combination that fits with what you're trying to portray. Also bare in mind that even though some colour schemes are known by everyone as standards it's always handy to have a legend to reinforce what they mean.