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