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