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