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