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