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