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