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