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