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