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