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