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