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