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