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