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)(13,14,17,18)(15,19,20,16)(22,25)(23,27)(6,7)(10,11)(13,15,17,20)(14,16,18,19)(22,25)(23,27)(8,12)(10,11)(14,18)(16,19)(21,22)(23,26)(24,25)(27,28) involution — undirected(1,2)(3,4)(5,7,9,6)(8,10,12,11)(13,15)(14,19)(16,18)(17,20)(5,8)(6,10)(7,11)(9,12)(13,16,17,19)(14,20,18,15)(21,23,24,27)(22,26,25,28)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.