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