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