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