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