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