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