CAPE is directly related to how warm the air parcel is relative to its surroundings for all elevations of its ascent and maps of CAPE can be used to estimate areas that should be expected to experience thunderstorms. In general, the greater the CAPE the more likely that thunderstorms will be strong or severe since CAPE relates directly to the strength of the thunderstorm updraft, which in turn relates to hail size. The green color means high potential for unstable air. Yellows and reds means there is enormous potential for unstable air. Finding areas of instability can help to show high possibilities for thunderstorms.
Thunderstorms usually come from unstable air.
The more deep primary colors, the hotter the temperature is than the air around it, the more unstable the air. There is a correspondence of the unstable areas shown on this chart to the regions of high dewpoint because dewpoint relates to the amount of water vapor present, which in turn relates to the amount of potential latent heat that can be released in ascending air parcels making them unstable.