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