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)(15,23)(16,26)(17,28)(18,20)(19,25)(21,27)(22,24) involution — undirected(1,2)(3,4)(7,12)(9,11)(13,15,17,25,18,16,24,27)(14,19,22,23,20,21,28,26)(5,7,8,12)(6,9,10,11)(14,20)(15,16)(22,28)(25,27)(2,4)(6,10)(9,11)(14,20)(15,16)(22,28)(25,27) involution — undirected(13,16,17,27,18,15,24,25)(14,21,22,26,20,19,28,23)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.