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