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