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