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)(15,22)(17,18)(21,27)(23,28)(24,26) involution — undirected(5,7)(6,9)(8,11)(10,12)(13,14,17,22,19,15,18,20)(16,21,26,28,25,23,24,27)(2,4)(7,11)(9,12)(13,15,18,22,19,14,17,20)(16,23,24,28,25,21,26,27)(7,11)(9,12)(13,16,19,25)(14,21,15,23)(17,26,18,24)(20,27,22,28)(6,10)(9,12)(13,17,19,18)(14,20,15,22)(16,24,25,26)(21,28,23,27)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.