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