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