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