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