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