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