Cold as a mountain stream How you know when your beer is cold enough and whether it's actually beer. Transcript Lighty Light mountain stream coldness indicator ad: What the advertiser wants you to think vs what you really need to know. Oh, wow, some unspecified cool coldness? Bring it! The colder the better! When the mountain stream turns blue, it's as cold as some mountain stream. If the can has that mountain stream, that's what the beer tastes like.