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