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