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