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