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