One vertex per element, one color per generator, with an edge from x to x·s.
(2,3)(5,6)(7,11)(8,12)(9,10)(13,14)(15,21)(16,19)(17,20)(18,22)(23,27)(24,26)(25,28) involution — undirected(2,3)(6,10)(11,12)(13,15,16,22)(14,18,19,21)(17,23,25,24)(20,26,28,27)(1,2,4,3)(5,7,9,8)(6,11,10,12)(14,19)(15,22)(20,28)(23,24)(1,3,4,2)(5,7,9,8)(6,11,10,12)(15,23)(17,25)(18,26)(20,28)(21,27)(22,24)(5,8,9,7)(6,11,10,12)(14,19)(18,21)(20,28)(26,27)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.