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