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