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