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