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