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