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