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)(15,19)(16,17)(18,20)(22,23)(24,25) involution — undirected(7,11)(10,12)(13,14)(15,19)(16,17)(18,20)(21,22,26,23)(24,27,25,28)(6,9)(10,12)(14,17)(18,19)(21,23,26,22)(24,27,25,28)(1,2)(3,4)(5,6)(7,10)(8,9)(11,12)(13,14)(15,18)(16,17)(19,20)(21,24,26,25)(22,27,23,28)(5,7)(6,10)(8,11)(9,12)(13,15)(14,18)(16,20)(17,19)(21,25,26,24)(22,28,23,27)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.