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