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