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