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