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)(13,14,20,18,19,23,17,28)(15,24,25,26,27,21,16,22)(5,6)(7,10)(8,11)(9,12)(13,15)(14,21)(16,17)(18,22)(19,27)(20,25)(23,24)(26,28) involution — undirected(2,4)(5,7,9,8)(6,10,12,11)(13,16,19,25)(14,22,23,26)(15,17,27,20)(18,24,28,21)(5,7,9,8)(6,11,12,10)(13,17,19,20)(14,18,23,28)(15,25,27,16)(21,26,24,22)(5,8,9,7)(6,11,12,10)(13,18,20,23,19,28,17,14)(15,26,25,21,27,22,16,24)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.