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