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