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