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