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