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