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