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