One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6)(7,11)(8,10)(9,12)(14,19)(15,23)(16,24)(22,27) involution — undirected(5,7,9,8)(6,10,12,11)(13,14)(15,21)(16,25)(17,19)(18,27)(20,24)(22,26)(23,28)(2,4)(5,7,9,8)(6,11,12,10)(13,15)(14,20)(16,18)(17,23)(19,25)(21,27)(22,28)(24,26)(5,8,9,7)(6,10,12,11)(15,24)(16,23)(18,26)(20,21)(22,27)(25,28)(13,16,17,24)(14,21,19,28)(15,18,23,26)(20,27,25,22)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.