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)(15,16)(17,20)(18,28)(19,23)(21,25)(22,24)(26,27) involution — undirected(1,2)(3,4)(5,6)(7,10)(8,9)(11,12)(13,15,24,27,19,25,18,17)(14,20,28,21,23,26,22,16)(6,9)(10,11)(13,16)(14,15)(17,22)(18,26)(19,21)(20,24)(23,25)(27,28) involution — undirected(2,4)(5,7,8,12)(6,10,9,11)(15,25)(16,21)(17,27)(20,26)(13,17,24,15,19,27,18,25)(14,21,28,26,23,16,22,20)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.