Mu Cephei is the famous "Garnet Star", so named by Sir William Herschel for its vivid red, even noticeable in binoculars (if somewhat more so in telescopes).

Mu is a semi-regular red supergiant. By definition semi-regulars have no set period, thus its variations, from 3.6 to 5.1 magnitudes, cannot be predicted.

To find mu Cephei place alpha Cephei at the top of your field of view. Toward the bottom will be mu Cephei: binoculars.