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