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