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