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