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