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