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