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