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