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