A method for granting access to change a security system from a locked state to an unlocked state includes: displaying a security access interface, wherein the security access interface comprises a graphical region, the graphical region is filled with a plurality of colors; selecting at least one color in the graphical region; at least recording at least one color property according to the at least one selected color; generating an input password at least according to the at least one recorded color property; determining whether the input password matches a predetermined password; and granting access if the input password matches with the predetermined password. A related security system is also provided.