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