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