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